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Zero population growth, sometimes abbreviated ZPG, is a condition of demographic balance where the number of people in a specified population neither grows nor declines; that is, the number of births plus in-migrants equals the number of deaths plus out-migrants. ZPG has been a prominent political movement since the 1960s. As part of the concept of optimum population, the movement considers zero population growth to be an objective towards which countries and the whole world should strive in the interests of accomplishing long-term optimal standards and conditions of living.Last, John M. "Zero Population Growth." Healthline. N.p., 2002. Web. 5 Oct. 2009. <>.


Definition

The growth rate of a population in a given year equals the number of births minus the number of deaths plus immigration minus emigration expressed as a percentage of the population at the beginning of the given year. For example, suppose a country begins a year with one million people and during the year experiences one hundred thousand births, eighty thousand deaths, one thousand immigrants and two hundred emigrants.  Change in population = 100,000 – 80,000 +1,000 – 200 = 20,800 Population growth rate = (20,800 ÷ 1,000,000) x 100% = 2.1% Zero population growth for a country occurs when the sum of these four numbers – births minus deaths plus immigration minus emigration - is zero. To illustrate, suppose a country begins the year with one million people and during the year experiences 85,000 births, 86,000 deaths, 1,500 immigrants and 500 emigrants.          Change in population = 85,000 – 86,000 + 1,500 – 500 = 0 Population growth rate = (0 ÷ 1,000,000) x 100% = 0% For the planet Earth as a whole, zero population growth occurs when the number of births equals the number of deaths.


History

The American sociologist and
demographer 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 ed ...
Kingsley Davis Kingsley Davis (August 20, 1908 – February 27, 1997) was an internationally recognized American sociologist and demographer. He was identified by the American Philosophical Society as one of the most outstanding social scientists of the twen ...
is credited with coining the term. However, it was used earlier by George J. Stolnitz, who stated that the concept of a stationary population dated back to 1693. A mathematical description was given by James Mirrlees. In the late 1960s, ZPG became a prominent political movement in the U.S. and parts of Europe, with strong links to environmentalism and feminism. Yale University was a stronghold of the ZPG activists who believed "that a constantly increasing population is responsible for many of our problems: pollution, violence, loss of values and of individual privacy." Prominent advocates of the movement were Paul Ehrlich, author of ''
The Population Bomb ''The Population Bomb'' is a 1968 book co-authored by Stanford University Professor emeritus Paul R. Ehrlich and Stanford senior researcher emeritus in conservation biology Anne Howland Ehrlich. It predicted worldwide famine due to overpopulati ...
'', Richard Bowers, a Connecticut lawyer, and Professor
Charles Lee Remington Charles Lee Remington (January 19, 1922 – May 31, 2007) was an American entomologist known for studies of butterflies and moths, a Yale University professor, and is considered the father of modern lepidoptery. He established a Periodical Ci ...
.


Effects

In the long term, zero population growth can be achieved when the
birth rate The birth rate for a given period is the total number of live human births per 1,000 population divided by the length of the period in years. The number of live births is normally taken from a universal registration system for births; populati ...
of a population equals the death rate. That is, the total fertility rate is at replacement level and birth and death rates are stable, a condition also called demographic equilibrium. Unstable rates can lead to drastic changes in population levels. This analysis is valid for the planet as a whole (assuming that
interplanetary travel Interplanetary spaceflight or interplanetary travel is the crewed or uncrewed travel between stars and planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the ...
remains at zero or negligible levels), but not necessarily for a region or country as it ignores
migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
. Even though the total fertility rate of a population reaches replacement level, that population will continue to change because of population momentum. A population that has been growing in the past will have a higher proportion of young people. As it is younger people who have children, there is large time lag between the point at which the fertility rate (mean total number of children each woman has during her childbearing years) falls to the replacement level (the fertility rate which would result in equal birth and death rates for a population at equilibrium) and the point at which the population stops rising. The reason for this is that even though the fertility rate has dropped to replacement level, people already continue to live for some time within a population. Therefore, equilibrium, with a static population, will not be reached until the first "replacement level" birth cohorts reach old age and die. The related calculations are complex because the population's overall death rate can vary over time, and mortality also varies with age (being highest among the old). Conversely, with fertility below replacement, a large elderly generation eventually results (as in an aging "
baby boom A baby boom is a period marked by a significant increase of birth rate. This demographic phenomenon is usually ascribed within certain geographical bounds of defined national and cultural populations. People born during these periods are often ca ...
"); but since that generation failed to replace itself during its fertile years, a subsequent "population bust", or decrease in population, will occur when the older generation dies off. This effect has been termed birth dearth. In addition, if a country's fertility is at replacement level, and has been that way for at least several decades (to stabilize its age distribution), then that country's population could still experience coincident growth due to continuously increasing
life expectancy Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of its birth, current age, and other demographic factors like sex. The most commonly used measure is life expectancy at birth ...
, even though the population growth is likely to be smaller than it would be from natural population increase. Zero population growth is often a goal of demographic planners and
environmentalist An environmentalist is a person who is concerned with and/or advocates for the protection of the environment. An environmentalist can be considered a supporter of the goals of the environmental movement, "a political and ethical movement that s ...
s who believe that reducing population growth is essential for the health of the ecosystem. Preserving cultural traditions and ethnic diversity is a factor for not allowing human populations levels or rates to fall too low. Achieving ZPG is difficult because a country's population growth is often determined by economic factors, incidence of poverty, natural disasters, disease, etc. However, even if there is zero population growth, there may be changes in demographics of great importance to economic factors, such as changes in age distribution.


Reaching zero population growth

Albert Bartlett, who was a professor of physics at the University of Colorado at Boulder, suggested that a population has the following choices to achieve ZPG: # Voluntarily limit births and immigration to achieve zero population growth; #Continue on the present path until the population is so large that draconian measures become necessary to stop the growth of population; #Do nothing and let nature stop the growth through disease, starvation, war, and pestilence. If humans do not solve the problem, nature will. Similarly, Jason Brent argues that there are three ways to achieve zero population growth. His argument is as follows: # By war, with or without weapons of mass destruction,
starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, ...
, disease, rape, murder,
ethnic cleansing Ethnic cleansing is the systematic forced removal of ethnic, racial, and religious groups from a given area, with the intent of making a region ethnically homogeneous. Along with direct removal, extermination, deportation or population transfer ...
,
concentration camps Internment is the imprisonment of people, commonly in large groups, without charges or intent to file charges. The term is especially used for the confinement "of enemy citizens in wartime or of terrorism suspects". Thus, while it can simp ...
, and other horrors beyond the imagination, when humanity has exceeded the
carrying capacity The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as ...
of the Earth. # By the voluntary action of all of humanity prior to the human population exceeding the carrying capacity of the Earth. If any group or even if a single-family failed to control its population the entire program would fail. # By coercive population control prior to the human population exceeding the carrying capacity of the Earth. A loosely defined goal of ZPG is to match the
replacement 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 ...
, which is the average number of children per woman which would hold the population constant. This replacement fertility will depend on
mortality rates Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of de ...
and the sex ratio at birth, and varies from around 2.1 in developed countries to over 3.0 in some developing countries.


In China

China is the largest country by population in the world, having some 1.4 billion people (as of 2021). China is expected to have a zero population growth rate by 2031. China's population growth has slowed since the beginning of this century. This has been mostly the result of China's economic growth and increasing living standards. However, many demographers also credit China's family planning policy, formulated in the early 1970s, that encouraged late marriages, late childbearing, and the use of contraceptives, and after 1980 limited most urban couples to one child and most rural couples to two children. According to government projections, the long-term effect of these policies will be a reduction of the working-age population to 700 million by 2050 vs 925 million in 2011, a decline of 24%. In November 2013, a relaxation of the one-child policy was announced amid unpopularity and the forecast of a reduced labor pool and support for an aging population.


In Europe


In Japan


See also

* Demographic transition * List of population concern organizations *
Overpopulation Overpopulation or overabundance is a phenomenon in which a species' population becomes larger than the carrying capacity of its environment. This may be caused by increased birth rates, lowered mortality rates, reduced predation or large scale ...
* Human population planning * Pledge two or fewer *
Steady-state economy A steady-state economy is an economy made up of a constant stock of physical wealth (capital) and a constant population size. In effect, such an economy does not grow in the course of time. The term usually refers to the national economy o ...
* World Scientists' Warning to Humanity *'' Z.P.G.''—A science-fiction movie concerning the topic of zero population growth.


References


Further reading

*


External links


Population Connection
{{DEFAULTSORT:Zero Population Growth Human overpopulation Population ecology Environmental controversies