Mass incarceration in America, explained in 22 maps and charts

Starting in the 1970s, America's incarcerated population began to rise rapidly. In response to a tide of higher crime over the preceding decade, state and federal lawmakers passed measures that increased the length of prison sentences for all sorts of crimes, from drugs to murder.

But around the mid-1990s, the crime rate began to drop as the number of incarcerated Americans continued to climb. After two decades of the crime decline, local, state, and federal lawmakers have begun to reconsider previous "tough on crime" policies — leading the prison population to drop for the first time in decades in 2010.

Chart credit: The Sentencing Project

Although the US makes up about 4 percent of the world's population, it accounts for 22 percent of the world's prison population. The US is out of line not only with its developed peers but also with authoritarian nations like Cuba, Russia, and China.

Part of the reason for America's high levels of incarceration is that the country has way more lethal crime than its developed peers. And unlike regimes like China, it makes less use of punitive punishments like the death sentence and forced evictions. But that doesn't explain the whole difference; studies have shown that US prison sentences are simply much longer than other nations'.

Map credit: German Lopez/Vox

Mass incarceration is, predominantly, black incarceration. Black people are nearly six times as likely to be incarcerated as white people, and nearly three times as likely to be incarcerated as their Latino counterparts.

Why? A review of the research by the Sentencing Project concluded that higher crime rates in black communities explained about 61 to 80 percent of black overrepresentation in prisons. This means that other factors, such as racial bias or past criminal records influencing prison sentences, were behind as much as 39 percent of the disparate rates of imprisonment for black people.

Chart credit: German Lopez/Vox

Black people are much more likely to be arrested for drugs, even though they're not more likely to use or sell them.

Chart credit: Joe Posner/Vox, with data from FBI Uniform Crime Reports and the US Census Bureau

Black defendants generally receive longer sentences than their white counterparts for the same crime. As the chart above demonstrates, this has been consistently true for drug trafficking. And a 2012 report from US Sentencing Commission found it to be true for other types of crimes, as well.

Chart credit: German Lopez/Vox

Most states don't let people in prison, on parole, or on probation vote, and 10 limit at least some felons from voting after they've completed their sentences, according to the American Civil Liberties Union.

As a result, more than 6.1 million Americans won't be legally allowed to vote due to their criminal records in 2016. Several states prohibited 5 to 11 percent of their electorate from voting. And since black Americans are likelier to go to prison, this had a disproportionate impact on the African-American electorate — leaving more than 20 percent of black voters in Florida, Kentucky, Tennessee, and Virginia legally banned from voting.

This is one of the various collateral effects of prison. Other examples include restrictions on employment and bans on receiving welfare benefits, accessing public housing, or qualifying for student loans for higher education.

Map credit: German Lopez/Vox

A lot of mainstream media attention goes to the federal prison system and war on drugs. But most people in prison are held at the state level, and they're usually in for violent offenses. This poses a very tricky situation for US policymakers: If they want to undo mass incarceration, they're going to have to cut back on the number of violent offenders in prison — but lawmakers have to figure out how to do that without endangering public safety.

Chart credit: German Lopez/Vox

Unlike the much larger state prison system, about half of federal prisoners are incarcerated for drug crimes. For federal lawmakers, this means much of the work of reducing the incarcerated population falls on cutting sentences for nonviolent drug offenses. But since the federal system is a relatively small part of the national system, those reforms would have a small impact on incarceration overall.

Chart credit: Joe Posner/Vox

Chart credit: Marshall Project

It's easy to look back with scorn at the "tough on crime" policies that fed mass incarceration: How could politicians really think that locking up millions of Americans would be a good idea?

But the chart above shows the vastly different circumstances lawmakers were working under at the time. America's murder and non-negligent manslaughter rate was historically very high, along with all violent and property crimes. As horror stories of gun violence and gang wars permeated the news, the public demanded that US leaders do something — leading to the "tough on crime" policies that are still with us today.

Chart credit: German Lopez/Vox

Map credit: MetricMaps

It's not just that prison sentences got longer; more crimes also began to be punished by life sentences, including life without parole, as prosecutors and judges embraced tougher sentences on some of the worst convicts. So not only are there more people in prison, but a record number are expected to spend the rest of their lives there.

Chart credit: The Sentencing Project

The problem isn't just longer prison sentences. As a result of "tough on crime" policies, more people are also being admitted to prison.

Since at least the 1990s, prosecutors have increasingly filed more charges for each arrest. So when someone was arrested by police, the prosecutor was generally more likely to file charges against that person in the 2000s than he or she was in the 1990s. This is one of the reasons — if not the reason — that admissions into prisons increased in the past few decades.

Criminologist John Pfaff cited several possible explanations for the trend, including political incentives to appear "tough on crime" and punitive policies strengthening prosecutors' ability to file charges. Whatever the cause, prosecutors now play a big role in driving mass incarceration.

Read more in Vox's explainer.

Chart credit: German Lopez/Vox

The war on drugs has played a significant — but exaggerated — role in mass incarceration. In particular, states and the federal government created lengthy mandatory minimum sentences for drug offenses. So someone is not only more likely to be arrested for drugs since the 1980s, but more likely to serve a lengthy prison sentence as well.

Chart credit: German Lopez/Vox, with data from Families Against Mandatory Minimums

Long after violent and property crimes began to drop in the 1990s, the US's incarceration rate continued to climb.

It's possible to look at this correlation and conclude that mass incarceration caused crime to drop.

But the research shows that incarceration reached the point of diminishing returns by the 1990s: A 2015 review of the evidence by the Brennan Center for Justice estimated that more incarceration explained 0 to 7 percent of the crime drop since the 1990s, while other researchers estimate it drove 10 to 25 percent of the crime drop since the '90s. After all, there are only so many serious criminals out there, and by the '90s the people getting put in prison weren't people who'd be committing crime after crime. So the US could very likely cut its incarceration rate without increasing crime much, if at all.

Chart credit: National Research Council

One way to see that mass incarceration has long reached the point of diminishing returns is by looking at the number of elderly people behind bars. Many people were handed down long prison sentences during their 20s and 30s, so they're now forced to remain in prison through their elderly years.

But how likely, really, is it that a 65-year-old would rob a bank and kill someone? The research suggests not very: People tend to age out of crime, particularly after their 20s and 30s, so letting them out of prison 10 or 20 years down the line — instead of 40 years, 50 years, or never — likely wouldn't pose a threat to public safety.

Not only has the imprisonment of the elderly driven up the incarceration rate, but it's actually made prison much more expensive — because elderly people tend to require more health care. According to the Washington Post's Sari Horwitz, the typical cost of a federal prisoner is about $27,500 a year, but older inmates cost nearly $59,000 each year.

Chart credit: Pew Charitable Trusts

Another way to gauge the diminishing benefits of prison is by looking at what happened in states after they reduced their prison populations in recent years. The data shows there's no correlation between imprisonment rates and crime, suggesting that states can bring down their prison populations without seriously risking public safety.

Chart credit: Christophe Haubursin and Matt Yglesias/Vox, with data from Pew Charitable Trusts

Even though incarceration is believed to have a small effect on crime rates, it's had a big effect on state budgets. All levels of government — but mostly state and local — spent more than $80 billion on corrections expenditures in 2010, according to the Hamilton Project.

Map credit: German Lopez/Vox

One bright spot in criminal justice reform: the juvenile justice system. The number of youth in residential detention has dropped by roughly half since 1999. The reforms at this level have been varied, including limits on how many juvenile offenders can be sent to adult prisons, a higher age requirement for some juvenile justice programs, and reductions on arrests for non-serious offenses at schools.

But the result is welcome: The juvenile justice system has seen a much bigger drop in its incarcerated population than the adult system. And it provides a model for the rest of the criminal justice system, since rates of incarceration fell alongside crime.

Chart credit: The Sentencing Project