Fertility factors are determinants of the number of children that an individual is likely to have.

Fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Fertili ...

factors are mostly positive or negative correlations without certain causations. Factors generally associated with increased fertility include the intention to have children, in advanced societies very high gender equality,

religiosity In sociology, the concept of religiosity has proven difficult to define. The Oxford English Dictionary suggests: "Religiousness; religious feeling or belief. ..Affected or excessive religiousness". Different scholars have seen this concept as ...

, inter-generational transmission of values,

marriage Marriage, also called matrimony or wedlock, is a culturally and often legally recognized union between people called spouses. It establishes rights and obligations between them, as well as between them and their children, and between ...

and

cohabitation Cohabitation is an arrangement where people who are not married, usually couples, live together. They are often involved in a romantic or sexually intimate relationship on a long-term or permanent basis. Such arrangements have become increas ...

, maternal and social support, rural residence, pro family government programs, low IQ and increased food production. Factors generally associated with decreased fertility include rising

income Income is the consumption and saving opportunity gained by an entity within a specified timeframe, which is generally expressed in monetary terms. Income is difficult to define conceptually and the definition may be different across fields. For ...

, value and attitude changes, education,

female labor participation Since the industrial revolution, participation of women in the workforce outside the home has increased in industrialized nations, with particularly large growth seen in the 20th century. Largely seen as a boon for industrial society, women in ...

population control Population control is the practice of artificially maintaining the size of any population. It simply refers to the act of limiting the size of an animal population so that it remains manageable, as opposed to the act of protecting a species from ...

, age,

contraception Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unwanted pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth contr ...

, partner reluctance to having children, very low level of gender equality, infertility,

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

, and

obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...

Factors associated with increased fertility

Intention

The predictive power of intentions continues to be debated. Research that argues that intentions are a good predictor of actual results tends to draw ideas from the

theory of planned behavior The theory of planned behavior (TPB) is a psychological theory that links beliefs to behavior. The theory maintains that three core components, namely, attitude, subjective norms, and perceived behavioral control, together shape an individua ...

(TPB). According to the TPB, intentions stem from three factors: attitudes regarding children, including the cost of raising them versus perceived benefits; subjective norms, for example the influence of others; and perceived control over behavior, that is, how much control an individual has over their own behavior. Fertility intentions tend to boil down to quantum intentions, or how many children to bear, and tempo intentions, meaning when to have them. Of these, quantum intention is the poor predictor because it tends to change as a result of the ups and downs of a typical life. Tempo intention is a somewhat better predictor, but still a weak way to predict actual results. The intention to have children generally increases the probability of having children. This relation is well evidenced in advanced societies, where

birth control Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unwanted pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth contr ...

is the default option. A comparison of a survey to birth registers in Norway found that parents were more likely to realize their fertility intentions than childless respondents. Part of the research project Family Dynamics, Fertility Choices and Family Policy (FAMDYN) It was also suggested that childless individuals may underestimate the effort of having children. On the other hand, parents may better understand their ability to manage another child. Individuals intending to have children immediately are more likely to achieve this within two years, whereas in contrast, the fertility rate was found to be higher among those intending to have children in the long term (after four years). Stability of fertility intentions further improves the chance to realize them. Such stability is increased by the belief that having a child will improve

life satisfaction Life satisfaction is a measure of a person's well-being, assessed in terms of mood, relationship satisfaction, achieved goals, self-concepts, and self-perceived ability to cope with life. Life satisfaction involves a favorable attitude towards on ...

and partner relationships. Chances of realizing fertility intentions are lower in

post-Soviet states The post-Soviet states, also known as the former Soviet Union (FSU), the former Soviet Republics and in Russia as the near abroad (russian: links=no, ближнее зарубежье, blizhneye zarubezhye), are the 15 sovereign states that wer ...

than in

Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...

an states. There are many determinants of the intention to have children, including: * The ''mother's preference'' of family size, which influences that of the children through early adulthood. Likewise, the

extended family An extended family is a family that extends beyond the nuclear family of parents and their children to include aunts, uncles, grandparents, cousins or other relatives, all living nearby or in the same household. Particular forms include the stem ...

influences fertility intentions, with an increased number of nephews and nieces increasing the preferred number of children. * ''Social pressure'' from kin and friends to have another child. * ''Social support''. A study from

West Germany West Germany is the colloquial term used to indicate the Federal Republic of Germany (FRG; german: Bundesrepublik Deutschland , BRD) between its formation on 23 May 1949 and the German reunification through the accession of East Germany on 3 O ...

found that both men receiving no support at all and receiving support from many different people have a lower probability of intending to have another child than those with a moderate degree of support. The negative effect of support from many different people is probably related to coordination problems. * ''Happiness'', with happier people tending to want more children. * ''A secure housing situation''. * ''Religiosity''.

Very high level of gender equality

In advanced societies, in which birth control is the default option, a more equal division of household tasks tends to improve chances for a second child. Equally, increases in employment equity tend to lead to a more equal division of household labor, and thus improve chances for a second child.

Fertility preference

The Preference Theory suggests that a woman's attitudes towards having children are shaped early in life. Furthermore, these attitudes tend to hold across the life course, and boil down to three main types: career-oriented, family-oriented, and a combination of both work and family. Research shows that family-oriented women have the most children, and work-oriented women have the least, or none at all, although causality remains unclear. Preferences can also apply to the sex of the children born, and can therefore influence the decisions to have more children. For instance, if a couple's preference is to have at least one boy and one girl, and the first two children born are boys, there is a significantly high likelihood that the couple will opt to have another child.

Religiosity

A survey taken place in 2002 in the United States found that women who reported

religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relates humanity to supernatural, ...

as "very important" in their everyday lives had a higher fertility than those reporting it as "somewhat important" or "not important". For many religions, religiosity is directly associated with an increase in the intention to have children. This appears to be the main means by which religion increases fertility.Pages 238-244
/ref> For example, as of 1963,

Catholic The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptized Catholics worldwide . It is among the world's oldest and largest international institutions, and has played a ...

couples generally had intentions to have more children than

Jewish Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...

couples, who in turn, tended to have more children than

Protestant Protestantism is a Christian denomination, branch of Christianity that follows the theological tenets of the Reformation, Protestant Reformation, a movement that began seeking to reform the Catholic Church from within in the 16th century agai ...

couples. Among Catholics, increased religiosity is associated with the intention to have more children, while on the other hand, increased religiousness among Protestants is associated with the intention to have fewer children. It has also been suggested that religions generally encourage lifestyles with fertility factors that, in turn, increase fertility. For example,

religious views on birth control Religious adherents vary widely in their views on birth control (also known as contraception). This can be true even between different branches of one faith, as in the case of Judaism and Christianity. Some religious believers find that their own ...

are, in many religions, more restrictive than secular views, and such religious restrictions have been associated with increased fertility. Religion sometimes modifies the fertility effects of education and income.

Catholic education Catholic education may refer to: * Catholic school, primary and secondary education organised by the Catholic Church or organisations affiliated with it * Catholic university, private university run by the Catholic Church or organisations affili ...

at the university level and the secondary school level is associated with higher fertility, even when accounting for the confounding effect that higher religiosity leads to a higher probability of attending a religiously affiliated school. Higher income is also associated with slightly increased fertility among Catholic couples, however, is associated with slightly decreased fertility among Protestant couples. Parents' religiosity is positively associated with their children's fertility. Therefore, more religious parents will tend to increase fertility. A 2020 study found that the relation between religiosity and fertility was driven by the lower aggregate fertility of secular individuals. While religiosity did not prevent low fertility levels (as some highly religious countries had low fertility rates), secularism did prevent high fertility (as no highly secular country had high fertility rates). Societal level secularism was also a better predictor of religious individuals' fertility than secular individuals, largely due to the effects of cultural values on reproduction, gender and personal autonomy.

Intergenerational transmission of values

The transmission of values from parents to offspring (

nurture Nature versus nurture is a long-standing debate in biology and society about the balance between two competing factors which determine fate: genetics (nature) and environment (nurture). The alliterative expression "nature and nurture" in English h ...

) has been a core area of fertility research. The assumption is that parents transmit these family values, preferences, attitudes and religiosity to their children, all of which have long-term effects analogous to genetics. Researchers have tried to find a causal relationship between, for example, the number of parents' siblings and the number of children born by the parents own children (a quantum effect), or between the age of the first birth of the parents' generation and age of first birth of any of their own children (a tempo effect). Most studies concerning tempo focus on teenage mothers and show that having had a young mother increases the likelihood of having a child at a young age. In

high-income countries A high-income economy is defined by the World Bank as a nation with a gross national income per capita of US$12,696 or more in 2020, calculated using the Atlas method. While the term "high-income" is often used interchangeably with "First World" a ...

, the number of children a person has strongly correlates with the number of children that each of those children will eventually have. Danish data from

non-identical twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

growing up in the same environment compared to

identical twin Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

s indicated that genetic influences in themselves largely override previously shared environmental influences. The

birth order Birth order refers to the order a child is born in their family; first-born and second-born are examples. Birth order is often believed to have a profound and lasting effect on psychological development. This assertion has been repeatedly challen ...

does not seem to have any effect on fertility. Other studies, however, show that this effect can be balanced by the child's own attitudes that result from personal experiences, religiosity, education, etc. So, although the mother's preference of family size may influence that of the children through early adulthood, the child's own attitudes then take over and influence fertility decisions.

Marriage and cohabitation

The effect of cohabitation on fertility varies across countries. In the US cohabitation is generally associated with lower fertility. However, another study found that cohabiting couples in France have equal fertility as married ones. Russians have also been shown to have a higher fertility within cohabitation. Survey data from 2003 in

Romania Romania ( ; ro, România ) is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern, and Southeast Europe, Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, S ...

showed that marriage equalized the

total fertility rate The total fertility rate (TFR) of a population is the average number of children that would be born to a woman over her lifetime if: # she were to experience the exact current age-specific fertility rates (ASFRs) through her lifetime # she were t ...

among both highly educated and limited-education people to approximately 1.4. Among those cohabiting, on the other hand, a lower level of education increased the fertility rate to 1.7, and a higher level of education decreased it to 0.7. Another study found that Romanian women with little education have about equal fertility in marital and cohabiting partnerships. A study of the United States, and multiple countries in Europe, found that women who continue to cohabit after giving birth have a significantly lower probability of having a second child than married women in all countries, except those in Eastern Europe.

Maternal support

Data from the Generations and Gender Survey showed that women with living mothers had earlier first births, while a mother's death early in a daughter's life correlated with a higher probability of childlessness. On the other hand, the survival of fathers had no effect on either outcome. Co-residence with parents delayed first births and resulted in lower total fertility and higher probability of childlessness. This effect is even stronger for poor women.

Social support

Social support from the extended family and friends can help a couple decide to have a child, or another one. Studies mainly in ex-communist Eastern European countries have associated increased fertility with increased

social capital Social capital is "the networks of relationships among people who live and work in a particular society, enabling that society to function effectively". It involves the effective functioning of social groups through interpersonal relationships ...

in the form of personal relationships, goods, information, money, work capacity, influence, power, and personal help from others. Research in the U.S. shows that the extended family willing to provide support becomes a "safety net". This is particularly important for single mothers and situations involving partnership instability. African family poses for a picture in the farm

African family poses for a picture in the farm

Rural residence

Total fertility rate The total fertility rate (TFR) of a population is the average number of children that would be born to a woman over her lifetime if: # she were to experience the exact current age-specific fertility rates (ASFRs) through her lifetime # she were t ...

s are higher among women in

rural area In general, a rural area or a countryside is a geographic area that is located outside towns and cities. Typical rural areas have a low population density and small settlements. Agricultural areas and areas with forestry typically are descri ...

s than among women in

urban area An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, t ...

s, as evidenced from

low-income Poverty is the state of having few material possessions or little

income

,Page 148
/ref> middle-income and

. Field researchers have found that fertility rates are high and remain relatively stable among rural populations. Little evidence exists to suggest that high-fertility parents appear to be economically disadvantaged, further strengthening the fact that total fertility rates tend to be higher among women in rural areas. On the other hand, studies have suggested that a higher

population density Population density (in agriculture: standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans, but sometimes to other living organisms too. It is a key geographical term.Matt RosenberPopul ...

is associated with decreased fertility rates. It is shown through studies that fertility rates differ between regions in ways that reflect the opportunity costs of child rearing. In a region with high population density, women restrain themselves from having many children due to the costs of living, therefore lowering the fertility rates. Within urban areas, people in

suburb A suburb (more broadly suburban area) is an area within a metropolitan area, which may include commercial and mixed-use, that is primarily a residential area. A suburb can exist either as part of a larger city/urban area or as a separate ...

s are consistently found to have higher fertility. Some research indicates that population density may explain up to 31% of the variance in fertility rates, although the effect of population density on fertility can be moderated by other factors such as environmental conditions, religiosity and social norms.

Pro-family government programs

Many studies have attempted to determine the causal link between government policies and fertility. However, as this article suggests, there are many factors that can potentially affect decisions to have children, how many to have, and when to have them, and separating these factors from effects of a particular government policy is difficult. Making this even more difficult is the time lag between government policy initiation and results. The purpose of these programs is to reduce the opportunity cost of having children, either by increasing family income or reducing the cost of children. One study has found a positive effect on number of children during life due to family policy programs that make it easier for women to combine family and employment. Again, the idea here is to reduce the opportunity cost of children. These positive results have been found in Germany, Sweden, Canada, and the U.S.Balbo 2013
(see top of list), citing: However, other empirical studies show that these programs are expensive and their impact tends to be small, so currently there is no broad consensus on their effectiveness in raising fertility.

Other factors associated with increased fertility

Other factors associated with increase of fertility include: * ''Social pressure'': Women have an increased probability to have another child when there is social pressure from parents, relatives, and friends to do so. For example, fertility increases during the one to two years after a sibling or a co-worker has a child. * ''

Patriarchy Patriarchy is a social system in which positions of dominance and privilege are primarily held by men. It is used, both as a technical anthropological term for families or clans controlled by the father or eldest male or group of males a ...

'': Male-dominated families generally have more children. * ''

Nuclear family A nuclear family, elementary family, cereal-packet family or conjugal family is a family group consisting of parents and their children (one or more), typically living in one home residence. It is in contrast to a single-parent family, the larger ...

households'' have higher fertility than cooperative living arrangements, according to studies both from the

Western World The Western world, also known as the West, primarily refers to the various nations and state (polity), states in the regions of Europe, North America, and Oceania.

. * ''Illegalization of abortion'' temporarily increased birth rates in communist Romania for a few years, but this was followed by a later decline due to an increased use of

illegal abortion Abortion laws vary widely among countries and territories, and have changed over time. Such laws range from abortion being freely available on request, to regulation or restrictions of various kinds, to outright prohibition in all circumstances ...

. * ''Immigration'' sometimes increases fertility rates of a country because of the births to the immigrant groups. However, over succeeding generations, migrant fertility often converges to that of their new country. * '' Assisted reproduction technology (ART).'' One study from Denmark projects an increase in fertility, as a result of ART, that could increase the 1975 birth cohort by 5%. In addition, ART seems to challenge the biological limits of successful childbearing. · * ''

Homophily Homophily () is a concept in sociology describing the tendency of individuals to associate and bond with similar others, as in the proverb "". The presence of homophily has been discovered in a vast array of network studies: over have observed ...

:'' an increased

fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Fertili ...

is seen in people with a tendency to seek acquaintance among those with common characteristics.

Factors associated with decreased fertility

Fertility is declining in advanced societies because couples are having fewer children or none at all, or they are delaying childbirth beyond the woman's most fertile years. The factors that lead to this trend are complex and probably vary from country to country.

Rising income

Increased

and

human development Human development may refer to: * Development of the human body * Developmental psychology * Human development (economics) * Human Development Index, an index used to rank countries by level of human development * Human evolution, the prehistoric ...

are generally associated with decreased fertility rates. Economic theories about declining fertility postulate that people earning more have a higher opportunity cost if they focus on childbirth and parenting rather than continuing their careers, that women who can economically sustain themselves have less incentive to become married, and that higher income parents value quality over quantity and so spend their resources on fewer children. On the other hand, there is some evidence that with rising economic development, fertility rates drop at first, but then begin to rise again as the level of social and economic development increases, while still remaining below the

replacement rate The total fertility rate (TFR) of a population is the average number of children that would be born to a woman over her lifetime if: # she were to experience the exact current age-specific fertility rates (ASFRs) through her lifetime # she were t ...

Value and attitude changes

While some researchers cite economic factors as the main driver of fertility decline, socio-cultural theories focus on changes in values and attitudes toward children as being primarily responsible. For example, the Second Demographic Transition reflects changes in personal goals, religious preferences, relationships, and perhaps most important, family formations. Also, Preference Theory attempts to explain how women's choices regarding work versus family have changed and how the expansion of options and the freedom to choose the option that seems best for them are the keys to recent declines in TFR. A comparative study in Europe found that family-oriented women had the most children, work-oriented women had fewer or no children, and that among other factors, preferences play a major role in deciding to remain childless. Another example of this can be found in Europe and in

, where values of increased autonomy and independence have been associated with decreased fertility.

Education

Results from research which attempts to find causality between education and fertility is mixed. One theory holds that higher educated women are more likely to become career women. Also, for higher educated women, there is a higher opportunity cost to bearing children. Both would lead higher educated women to postpone marriage and births. However, other studies suggest that, although higher educated women may postpone marriage and births, they can recuperate at a later age so that the impact of higher education is negligible. In the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, a large survey found that women with a bachelor's degree or higher had an average of 1.1 children, while those with no high school diploma or equivalent had an average of 2.5 children. For men with the same levels of education, the number of children was 1.0 and 1.7, respectively. In

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, on the other hand, women who are more educated eventually have about as many children as do the less educated, but that education results in having children at an older age. Likewise, a study in

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

found that better-educated males have a decreased probability of remaining childless, although they generally became fathers at an older age.

at the university level and, to a lesser degree, at the secondary school level, is associated with higher fertility, even when accounting for the confounding effect that higher religiosity among Catholics leads to a higher probability of attending a religiously affiliated school. The level of a country's development often determines the level of women's education required to affect fertility. Countries with lower levels of development and gender equivalence are likely to find that a higher level of women's education, greater than secondary level, is required to affect fertility. Studies suggest that in many sub-Saharan African countries fertility decline is linked to female education. Having said this, fertility in undeveloped countries can still be significantly reduced in the absence of any improvement in the general level of formal education. For example, During the period 1997-2002 (15 years), fertility in Bangladesh fell by almost 40 per cent, despite the fact that literacy rates (especially those of women) did not increase significantly. This reduction has been attributed to that country's family planning program, which could be called a form of informal education.

Population control

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

and

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

have the oldest and the largest

human population control Human population planning is the practice of intentionally controlling the growth rate of a human population. The practice, traditionally referred to as population control, had historically been implemented mainly with the goal of increasing po ...

programs in the world. In China, a

one-child policy The term one-child policy () refers to a population planning initiative in China implemented between 1980 and 2015 to curb the country's population growth by restricting many families to a single child. That initiative was part of a much br ...

was introduced between 1978 and 1980, and began to be formally phased out in 2015 in favor of a two-child policy. The

fertility rate The total fertility rate (TFR) of a population is the average number of children that would be born to a woman over her lifetime if: # she were to experience the exact current age-specific fertility rates (ASFRs) through her lifetime # she were t ...

in China fell from 2.8 births per woman in 1979 to 1.5 in 2010. However, the efficacy of the one-child policy itself is not clear, since there was already a sharp reduction from more than five births per woman in the early 1970s, before the introduction of the one-child policy. It has thereby been suggested that a decline in fertility rate would have continued even without the strict antinatalist policy. As of 2015, China has ended its decade long one child police allowing couples to have two children. This was a result of China having a large

dependency ratio The dependency ratio is an age-population ratio of those typically not in the labor force (the ''dependent'' part ages 0 to 14 and 65+) and those typically in the labor force (the ''productive'' part ages 15 to 64). It is used to measure the press ...

with its ageing population and working force. Extensive efforts have been put into

family planning in India Family planning in India is based on efforts largely sponsored by the Indian government. From 1965 to 2009, contraceptive usage has more than tripled (from 13% of married women in 1970 to 48% in 2009) and the fertility rate has more than halve ...

. The fertility rate has dropped from 5.7 in 1966 to 2.4 in 2016. Still, India's family planning program has been regarded as only partially successful in controlling fertility rates.

Female labor force participation

Increased participation of

women in the workforce Since the industrial revolution, participation of women in the workforce outside the home has increased in industrialized nations, with particularly large growth seen in the 20th century. Largely seen as a boon for industrial society, women in ...

is associated with decreased fertility. A multi-country

panel study A longitudinal study (or longitudinal survey, or panel study) is a research design that involves repeated observations of the same variables (e.g., people) over short or long periods of time (i.e., uses longitudinal data). It is often a type of obs ...

found this effect to be strongest among women aged 20–39, with a less strong but persistent effect among older women as well. International

United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and international security, security, develop friendly relations among nations, achieve international cooperation, and be ...

data suggests that women who work because of economic necessity have higher fertility than those who work because they want to do so. However, for countries in the

OECD The Organisation for Economic Co-operation and Development (OECD; french: Organisation de coopération et de développement économiques, ''OCDE'') is an intergovernmental organisation with 38 member countries, founded in 1961 to stimulate e ...

area, increased female labor participation has been associated with increased fertility. Causality analyses indicate that fertility rate influences female labor participation, not the other way around. Women who work in nurturing professions such as teaching and health generally have children at an earlier age. It is theorized that women often self-select themselves into jobs with a favorable

work–life balance Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking ** Working animal, an animal tr ...

in order to pursue both motherhood and employment.

Age

Regarding

age and female fertility Female fertility is affected by age and is a major fertility factor for women. A woman's fertility peaks between the late teens and late-20s, after which it starts to decline slowly. While many sources suggest a more dramatic drop at around 35, ...

, fertility starts at onset of menses, typically around age 12-13 Most women become

subfertile Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). It is the normal stat ...

during the early 30s, and during the early 40s most women become sterile. Regarding age and male fertility, men have decreased pregnancy rates, increased time to pregnancy, and increased infertility as they age, although the correlation is not as substantial as in women. When controlling for the age of the female partner, comparisons between men under 30 and men over 50 found relative decreases in pregnancy rates between 23% and 38%. An Indian study found that couples where the woman is less than one year younger than the man have a total mean number of children of 3.1, compared to 3.5 when the woman is 7–9 years younger than the man.

Contraception

The "contraceptive revolution" has played a crucial role in reducing the number of children (quantum) and postponing child-bearing (tempo). Periods of decreased use of

contraceptive pill Oral contraceptives, abbreviated OCPs, also known as birth control pills, are medications taken by mouth for the purpose of birth control. Female Two types of female oral contraceptive pill, taken once per day, are widely available: * The combin ...

s due to fears of side effects have been linked with increased fertility in the United Kingdom. Introductions of laws that increase access to contraceptives have been associated with decreased fertility in the United States. However, short-term decreases in fertility may reflect a

tempo effect Sub-replacement fertility is a total fertility rate (TFR) that (if sustained) leads to each new generation being less populous than the older, previous one in a given area. The United Nations Population Division defines sub-replacement fertilit ...

of later childbearing, with individuals using contraceptives catching up later in life. A review of long-term fertility in Europe did not find fertility rates to be directly affected by availability of contraceptives.

Partner and partnership

The decision to bear a child in advanced societies generally requires agreement between both partners. Disagreement between partners may mean that the desire for children of one partner are not realized. The last several decades have also seen changes in partnership dynamics. This has led to a tendency toward later marriages and a rise in unmarried cohabitation. Both of these have been linked to the postponement of parenthood (tempo) and thus reduced fertility.

Very low level of gender equality

The effects differed across countries. A study comparing gender equality in the Netherlands with that of Italy found that an unequal division of household work can significantly reduce a woman's interest in having children. Another study focused on quality of life of women in Canada found that women who felt overburdened at home tended to have fewer children. Another study found a U-shaped relationship between gender equity within the couple and fertility with higher probability of having a second child in families with either very low or very high gender equality.

Infertility

20-30% percent of infertility cases are due to male infertility, 20–35% are due to

female infertility Female infertility refers to infertility in women. It affects an estimated 48 million women, with the highest prevalence of infertility affecting women in South Asia, Sub-Saharan Africa, North Africa/Middle East, and Central/Eastern Europe and Cen ...

, and 25-40% are due to combined problems. In 10–20% of cases, no cause is found. The most common cause of

is ovulatory problems, which generally manifest themselves by sparse or absent menstrual periods. Male infertility is most commonly caused by deficiencies in the

semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen i ...

semen quality Semen quality is a measure of male fertility, a measure of the ability of sperm in semen to accomplish fertilization. Semen quality involves both sperm quantity and quality Cryptorchidism, hypospadias, testicular cancer and poor semen quali ...

is used as a surrogate measure of male fecundity.

Other factors associated with decreased fertility

* ''Intense relationships''. A Dutch study found that couples are likely to have fewer children if they have high levels of either negative or positive interaction. * ''Unstable relationships'', according to a

review A review is an evaluation of a publication, product, service, or company or a critical take on current affairs in literature, politics or culture. In addition to a critical evaluation, the review's author may assign the work a rating to indi ...

in Europe. * ''Higher tax rates''. * ''Unemployment''. A study in the USA shows that unemployment in women has effects both in the short and the long term in reducing their fertility rate. * ''Generosity of public pensions''. It has been theorized that social security systems decrease the incentive to have children to provide security in old age.

Factors of no or uncertain effect

Delayed childbearing

The trend of couples forming partnerships and marrying at later ages has been going on for some time. For example, in the US, during the period 1970 to 2006, the average age of first-time mothers increased by 3.6 years, from 21.4 years to 25.0 years. Also, fertility postponement has become common in all European countries, including those of the former Soviet Union. Nevertheless, delayed childbirth alone is not sufficient to reduce fertility rates: in France despite the average high age at first birth, fertility rate remains close to the 2.1 replacement value. The aggregate effects of delayed childbearing tend to be relatively minor, because most women still have their first child well before the onset of infertility.

Intelligence

The relationship between

fertility and intelligence The relationship between fertility and intelligence has been investigated in many demographic studies. There is evidence that, on a population level, measures of intelligence such as educational attainment and literacy are negatively correlated w ...

has been investigated in many

demographic Demography () is the statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...

studies; there is no conclusive evidence of a positive or negative correlation between human intelligence and fertility rate.

Other factors of no or uncertain effect

The following have been reported, at least in the primary research literature, to have no or uncertain effects. * ''

Personality Personality is the characteristic sets of behaviors, cognitions, and emotional patterns that are formed from biological and environmental factors, and which change over time. While there is no generally agreed-upon definition of personality, mos ...

''. One study found no consequential associations between personality and fertility, with tested traits including

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

, nurturance needs,

delayed gratification Delayed gratification, or deferred gratification, is the resistance to the temptation of an immediate pleasure in the hope of obtaining a valuable and long-lasting reward in the long-term. In other words, delayed gratification describes the pro ...

self-awareness In philosophy of self, self-awareness is the experience of one's own personality or individuality. It is not to be confused with consciousness in the sense of qualia. While consciousness is being aware of one's environment and body and lifesty ...

, compulsiveness,

ambiguity tolerance Ambiguity is the type of meaning in which a phrase, statement or resolution is not explicitly defined, making several interpretations plausible. A common aspect of ambiguity is uncertainty. It is thus an attribute of any idea or statement ...

cooperativeness Cooperativeness is a personality trait concerning the degree to which a person is generally agreeable in their relations with other people as opposed to aggressively self-centred and hostile. It is one of the "character" dimensions in Cloninger's ...

, and

need for achievement Need for achievement (N-Ach) is an individual's desire for significant accomplishment, mastering of skills, control, or high standards. The term was first used by Henry Murray and associated with a range of actions. These include: "intense, prolonge ...

. * ''Government support of assisted reproductive technology'', policies that transfer cash to families for pregnancy, and child support have only a limited effect on total fertility rate, according to the same review. * ''Relationship quality and stability'' have complex relations to fertility, wherein couples with a medium-quality relationship appear to be the most likely to have another child. * ''Governmental maternity leave benefits'' have no significant effect on fertility, according to one primary source. * ''Children from previous unions''. A study in the United Kingdom found that partners with children from previous unions have a higher likelihood of having children together. A study in France found the opposite, that childbearing rates are lowest after repartnering if both partners are already parents. The French study also found that in couples where only one was already a parent, fertility rates were about the same as in childless couples. * ''Spousal height difference''. * ''Mother's health'' is also a great determinant of the state of health of the unborn child, mother's death in childbirth means almost certain death for her newly born child. * ''Birth spacing'' refers to the timing and frequency of pregnancies. Child birth to a mother is affected by this factor in one way or the other. * ''Familism.'' The fertility impact is unknown in country-level

familism Familialism or familism is an ideology that puts priority to family. The term ''familialism'' has been specifically used for advocating a welfare system wherein it is presumed that families will take responsibility for the care of their members ...

systems, where the majority of the economic and caring responsibilities rest on the family (such as in Southern Europe), as opposed to defamilialized systems, where welfare and caring responsibilities are largely supported by the state (such as Nordic countries).

Racial and ethnic factors

In the

Hispanic The term ''Hispanic'' ( es, hispano) refers to people, Spanish culture, cultures, or countries related to Spain, the Spanish language, or Hispanidad. The term commonly applies to countries with a cultural and historical link to Spain and to Vic ...

s, and

African American African Americans (also referred to as Black Americans and Afro-Americans) are an ethnic group consisting of Americans with partial or total ancestry from sub-Saharan Africa. The term "African American" generally denotes descendants of ens ...

s have earlier and higher fertility than other racial and ethnic groups. In 2009, the teen birth rate for Hispanics between the age 15-19 was roughly 80 births per 1000 women. The teen birth rate for African Americans in 2009 was 60 births per 1000 women and 20 for non Hispanic teens (white). According to the United States census, State Health Serve and the CDC, Hispanics accounted for 23% of the birth in 2014 out of the 1,000,000 births in the United States.

Multifactorial analyses

regression analysis In statistical modeling, regression analysis is a set of statistical processes for estimating the relationships between a dependent variable (often called the 'outcome' or 'response' variable, or a 'label' in machine learning parlance) and one ...

on a population in India resulted in the following equation of

, where parameters preceded by a plus were associated with increased fertility, and parameters preceded by a minus were associated with decreased fertility: Total Fertility Rate = 0.02 ( human development index*) + 0.07 ( infant mortality rate*) − 0.34 (

contraceptive Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unwanted pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth contr ...

use) + 0.03 (male age at marriage*) − 0.21 (female age at marriage) − 0.16 (birth interval) − 0.26 (use of improved water quality) + 0.03 (male literacy rate*) − 0.01 (female literacy rate*) − 0.30 ( maternal care) * = Parameter did not reach statistical significance on its own