In October 2013, the incarceration rate of the United States of America was the highest in the world, at 716 per 100,000 of the national population. While the United States represents about 4.4 percent of the world's population, it houses around 22 percent of the world's prisoners. Corrections (which includes prisons, jails, probation, and parole) cost around $74 billion in 2007 according to the U.S. Bureau of Justice Statistics.
In 2016, the Prison Policy Initiative estimated that in the United States, about 2,298,300 people were incarcerated out of a population of 323.1 million. This means that 0.71% of the population was behind bars. Of those who were incarcerated, about 1,351,000 people were in state prison, 646,000 in local jails, 211,000 in federal prisons, 34,000 in youth correctional facilities, 33,000 in immigration detention camps, 14,000 in territorial prisons, 5,500 in civil commitment, 2,400 in Indian country jails, and 1,400 in United States military prisons.
Total U.S. incarceration (prisons and jails) peaked in 2008. Total correctional population peaked in 2007. If all prisoners are counted (including those juvenile, territorial, U.S. Immigration and Customs Enforcement (ICE) (immigration detention), Indian country, and military), then in 2008 the United States had around 24.7% of the world's 9.8 million prisoners.
The United States has the highest documented incarceration rate in the world, at 754 per 100,000 (as of 2009[update]). As of December 31, 2010, the International Centre for Prison Studies (ICPS) at King's College London estimated 2,266,832 prisoners from a total population of 310.64 million as of this date (730 per 100,000 in 2010).
This number comprises local jails with a nominal capacity of 866,782 inmates occupied at 86.4% (June 6, 2010), state prisons with a nominal capacity of approximately 1,140,500 occupied at approximately 115% (December 31, 2010), and federal prisons with a nominal capacity of 126,863 occupied at 136.0% (December 31, 2010). Of this number, 21.5% are pretrial detainees (December 31, 2010), 8.7% are female prisoners (December 31, 2010), 0.4% are juveniles (June 6, 2009), and 5.9% are foreign prisoners (June 30, 2007).
The imprisonment rate varies widely by state; Louisiana surpasses this by about 100%, but Maine incarcerates at about a fifth this rate. A report released 28 February 2008, indicates that more than 1 in 100 adults in the United States are in prison.
According to a U.S. Department of Justice report published in 2006, over 7.2 million people were at that time in prison, on probation, or on parole (released from prison with restrictions). That means roughly 1 in every 32 adult Americans are under some sort of criminal justice system control.
In the last forty years, incarceration has increased with rates upwards of 500% despite crime rates decreasing nationally. Between the years 2001 and 2012, crime rates (both property and violent crimes) have consistently declined at a rate of 22% after already falling an additional 30% in years prior between 1991 and 2001. As of 2012, there are 710 people per every 100,000 U.S. residents in the United States that are imprisoned in either local jails, state prisons, federal prisons, and privately operated facilities. This correlates to incarcerating a number close to almost a quarter of the prison population in the entire world. Mass incarceration is an intervening variable to more incarceration.
The Bureau of Justice Statistics has released a study which finds that, despite the total number of prisoners incarcerated for drug-related offenses increasing by 57,000 between 1997 and 2004, the proportion of drug offenders to total prisoners in State prison populations stayed steady at 21%. The percentage of Federal prisoners serving time for drug offenses declined from 63% in 1997 to 55% in that same period. In the twenty-five years since the passage of the Anti-Drug Abuse Act of 1986, the United States penal population rose from around 300,000 to more than two million. Between 1986 and 1991, African-American women's incarceration in state prisons for drug offenses increased by 828 percent.
In 2009, the U.S. Department of Justice announced that the growth rate of the state prison population had fallen to its lowest since 2006, but it still had a 0.2% growth-rate compared to the total U.S. prison population. The California state prison system population fell in 2009, the first year that populations had fallen in 38 years.
When looking at specific populations within the criminal justice system the growth rates are vastly different. In 1977, there were just slightly more than eleven thousand incarcerated women. By 2004, the number of women under state or federal prison had increased by 757 percent, to more than 111,000, and the percentage of women in prison has increased every year, at roughly double the rate of men, since 2000. The rate of incarcerated women has expanded at about 4.6% annually between 1995 and 2005 with women now accounting for 7% of the population in state and federal prisons.
Comparing some countries with similar percentages of immigrants, Germany has an incarceration rate of 76 per 100,000 population (as of 2014), Italy is 85 per 100,000 (as of 2015), and Saudi Arabia is 161 per 100,000 (as of 2013). Comparing other countries with a zero tolerance policy for illegal drugs, the rate of Russia is 455 per 100,000 (as of 2015), Kazakhstan is 275 per 100,000 (as of 2015), Singapore is 220 per 100,000 (as of 2014), and Sweden is 60 per 100,000 (as of 2014).
A 2014 report by the National Research Council identified two main causes of the increase in the United States' incarceration rate over the previous 40 years: longer prison sentences and increases in the likelihood of imprisonment. The same report found that longer prison sentences were the main driver of increasing incarceration rates since 1990.
Even though there are other countries that commit more inmates to prison annually, the fact that the United States keeps their prisoners longer causes the total rate to become higher. To give an example, the average burglary sentence in the United States is 16 months, compared to 5 months in Canada and 7 months in England.
Looking at reasons for imprisonment will further clarify why the incarceration rate and length of sentences are so high. The practice of imposing longer prison sentences on repeat offenders is common in many countries but the three-strikes laws in the U.S. with mandatory 25 year imprisonment — implemented in many states in the 1990s — are statutes enacted by state governments in the United States which mandate state courts to impose harsher sentences on habitual offenders who are previously convicted of two prior serious criminal offenses and then commit a third.
Crime rates in low-income areas are much higher than in middle to high class areas. As a result, Incarceration rates in low-income areas are much higher than in wealthier areas due to these high crime rates. When the incarcerated or criminal is a youth, there is a significant impact on the individual and rippling effects on entire communities. Social capital is lost when an individual is incarcerated. How much social capital is lost is hard to accurately estimate, however Aizer and Doyle found a strong positive correlation between lower income as an adult if an individual is incarcerated in their youth in comparison to those who are not incarcerated. 63 percent to 66 percent of those involved in crimes are under the age of thirty. People incarcerated at a younger age lose the capability to invest in themselves and in their communities. Their children and families become susceptible to financial burden preventing them from escaping low-income communities. This contributes to the recurring cycle of poverty that is positively correlated with incarceration. Poverty rates have not been curbed despite steady economic growth. Poverty is not the sole dependent variable for increasing incarceration rates. Incarceration leads to more incarceration by putting families and communities at a dynamic social disadvantage.
The "War on Drugs" is a policy that was initiated by Richard Nixon with the Comprehensive Drug Abuse Prevention and Control Act of 1970 and vigorously pursued by Ronald Reagan. By 2010, drug offenders in federal prison had increased to 500,000 per year, up from 41,000 in 1985. According to Michelle Alexander, drug related charges accounted for more than half the rise in state prisoners between 1985 and 2000. 31 million people have been arrested on drug related charges, approximately 1 in 10 Americans. In contrast, John Pfaff of Fordham Law School has accused Alexander of exaggerating the influence of the War on Drugs on the rise in the United States' incarceration rate: according to him, the percent of state prisoners whose primary offense was drug-related peaked at 22% in 1990. The Brookings Institution reconciles the differences between Alexander and Pfaff by explaining two ways to look at the prison population as it relates to drug crimes, concluding "The picture is clear: Drug crimes have been the predominant reason for new admissions into state and federal prisons in recent decades" and "rolling back the war on drugs would not, as Pfaff and Urban Institute scholars maintain, totally solve the problem of mass incarceration, but it could help a great deal, by reducing exposure to prison." 
After the passage of Reagan's Anti-Drug Abuse Act in 1986, incarceration for non-violent offenses dramatically increased. The Act imposed the same five-year mandatory sentence on those with convictions involving crack as on those possessing 100 times as much powder cocaine. This had a disproportionate effect on low-level street dealers and users of crack, who were more commonly poor blacks, Latinos, the young, and women.
Courts were given more discretion in sentencing by the Kimbrough v. United States (2007) decision, and the disparity was decreased to 18:1 by the Fair Sentencing Act of 2010. As of 2006[update], 49.3% of state prisoners, or 656,000 individuals, were incarcerated for non-violent crimes. As of 2008[update], 90.7% of federal prisoners, or 165,457 individuals, were incarcerated for non-violent offenses.
By 2003, 58% of all women in federal prison were convicted of drug offenses. Black and Hispanic women in particular have been disproportionately affected by the War on Drugs. Since 1986, incarceration rates have risen by 400% for women of all races, while rates for Black women have risen by 800%. Formerly incarcerated Black women are also most negatively impacted by the collateral legal consequences of conviction.
According to the American Civil Liberties Union, "Even when women have minimal or no involvement in the drug trade, they are increasingly caught in the ever-widening net cast by current drug laws, through provisions of the criminal law such as those involving conspiracy, accomplice liability, and constructive possession that expand criminal liability to reach partners, relatives and bystanders."
These new policies also disproportionately affect African-American women. According to Dorothy E. Roberts, the explanation is that poor women, who are disproportionately black, are more likely to be placed under constant supervision by the State in order to receive social services. They are then more likely to be caught by officials who are instructed to look specifically for drug offenses. Roberts argues that the criminal justice system's creation of new crimes has a direct effect on the number of women, especially black women, who then become incarcerated.
One of the first laws in the U.S. against drugs was the Opium Exclusion Act of 1909. It prohibited the smoking of opium, which was ingested but not smoked by a substantial portion of caucasian housewives in America. It was smoked mainly by Asian American immigrants coming to build the railroads. These immigrants were targeted with anti-Asian sentiment, as many voters believed they were losing jobs to Asian immigrants.
This pattern was repeated in the late twentieth century with higher penalties for crack cocaine than powder. Crack was consumed primarily by African Americans, while powder was consumed more by the white middle-class. The substantial penalties for crack contributed to the five-fold increase in incarcerations seen in the plot above. For instance, the disproportionate number of African Americans compared to other racial groups in the United States that are arrested or incarcerated. Figures from 2008 offer a better illustration of the situation with 28% of arrests involving African Americans and African American men comprising almost half of the current incarcerated population in the United States.
In the 1980s, the rising number of people incarcerated as a result of the War on Drugs and the wave of privatization that occurred under the Reagan Administration saw the emergence of the for-profit prison industry. Prior to the 1980s, private prisons did not exist in the US.
In a 2011 report by the ACLU, it is claimed that the rise of the for-profit prison industry is a "major contributor" to "mass incarceration," along with bloated state budgets. Louisiana, for example, has the highest rate of incarceration in the world with the majority of its prisoners being housed in privatized, for-profit facilities. Such institutions could face bankruptcy without a steady influx of prisoners. A 2013 Bloomberg report states that in the past decade the number of inmates in for-profit prisons throughout the U.S. rose 44 percent.
Corporations who operate prisons, such as the Corrections Corporation of America and The GEO Group, spend significant amounts of money lobbying the federal government along with state governments. The two aforementioned companies, the largest in the industry, have been contributors to the American Legislative Exchange Council (ALEC), which seeks to expand the privatization of corrections and lobbies for policies that would increase incarceration, such as three-strike laws and “truth-in-sentencing” legislation. Prison companies also sign contracts with states that guarantee at least 90 percent of prison beds be filled. If these "lockup quotas" aren't met, the state must reimburse the prison company for the unused beds. Prison companies use the profits to expand and put pressure on lawmakers to incarcerate a certain number of people. This influence on the government by the private prison industry has been referred to as the Prison–industrial complex.
The industry is well aware of what reduced crime rates could mean to their bottom line. This from the CCA's SEC report in 2010:
Our growth … depends on a number of factors we cannot control, including crime rates … [R]eductions in crime rates … could lead to reductions in arrests, convictions and sentences requiring incarceration at correctional facilities.
A substantial body of research claims that incarceration rates are primarily a function of media editorial policies, largely unrelated to the actual crime rate. Constructing Crime: Perspectives on Making News and Social Problems is a book collecting together papers on this theme. The researchers say that the jump in incarceration rate from 0.1% to 0.5% of the United States population from 1975 to 2000 (documented in the figure above) was driven by changes in the editorial policies of the mainstream commercial media and is unrelated to any actual changes in crime. Media consolidation reduced competition on content. That allowed media company executives to maintain substantially the same audience while slashing budgets for investigative journalism and filling the space from the police blotter, which tended to increase and stabilize advertising revenue. It is safer, easier and cheaper to write about crimes committed by poor people than the wealthy. Poor people can be libeled with impunity, but major advertisers can materially impact the profitability of a commercial media organization by reducing their purchases of advertising space with that organization.
News media thrive on feeding frenzies (such as missing white women) because they tend to reduce production costs while simultaneously building an audience interested in the latest development in a particular story. It takes a long time for a reporter to learn enough to write intelligently about a specific issue. Once a reporter has achieved that level of knowledge, it is easier to write subsequent stories. However, major advertisers have been known to spend their advertising budgets through different channels when they dislike the editorial policies. Therefore, a media feeding frenzy focusing on an issue of concern to an advertiser may reduce revenue and profits.
Sacco described how "competing news organizations responded to each other's coverage [while] the police, in their role as gatekeepers of crime news, reacted to the increased media interest by making available more stories that reflected and reinforced" a particular theme. "[T]he dynamics of competitive journalism created a media feeding frenzy that found news workers 'snatching at shocking numbers' and 'smothering reports of stable or decreasing use under more ominous headlines.'"
The reasons cited above for increased incarcerations (US racial demographics, Increased sentencing laws, and Drug sentencing laws) have been described as consequences of the shift in editorial policies of the mainstream media.
Additionally, media coverage has been proven to have a profound impact on criminal sentencing. A study conducted found that the more media attention a criminal case is given, the greater the incentive for prosecutors and judges to pursue harsher sentences. This is directly linked to the enormous increase in media coverage of crime over the past two decades. While crime decreased by 8% between 1992 and 2002, news reports on crime increased by 800% and the average prison sentence length increased by 2,000% for all crimes. Less media coverage means a greater chance of a lighter sentence or that the defendant may avoid prison time entirely.
According to the Federal Bureau of Prisons, 77.6% of Federal inmates are U.S. citizens (as of April 2016). 15.2% are citizens of Mexico, and the next three countries—Colombia, Cuba, and the Dominican Republic, contribute less than 1% each. 4.9% have other or unknown citizenship. The Bureau did not state how many had come to the U.S. legally.