ERIC HOLDER and Rick Perry (pictured) have little in common. America’s attorney-general is black, liberal and uses the word “community” a lot. The governor of Texas is white, conservative and says “God” a lot. Last month Mr Holder’s Justice Department sued Texas for allegedly trying to make it harder for blacks to vote. Last year Mr Perry ran to unseat Mr Holder’s boss, Barack Obama.

On one thing, however, the two men agree. On August 12th Mr Holder said: “Too many Americans go to too many prisons for far too long, and for no truly good law-enforcement reason.” He then unveiled reforms to reduce the number of people sent to America’s overcrowded federal prisons. In this, he was following the perfectly-coiffed Texan’s lead. Several years ago, Mr Perry enacted similar reforms in the Lone Star State, and they worked.

America has the world’s largest prison population. China, which has more than four times as many people and nobody’s idea of a lenient judiciary, comes a distant second. One in 107 American adults was behind bars in 2011—the highest rate in the world—and one in every 34 was under “correctional supervision” (either locked up or on probation or parole). A black man in America is 3.6 times more likely to be incarcerated than a black man in 1993 in South Africa, just before apartheid ended.

Granted, the number of Americans under lock and key has fallen since 2008, but only from 2.31m to 2.24m. And that slight dip comes after a mammoth rise: between 1980 and 2008, the number of incarcerated Americans more than tripled.

In the federal prison system, for which Mr Holder is responsible, the rise has been even more dramatic (see chart). From the 1940s to the early 1980s the federal prison population remained relatively stable, at around 24,000. But then came the crack epidemic, to which Congress responded with mandatory-minimum sentences. A first-time offender convicted of possessing five grams of crack, for instance, received a mandatory-minimum sentence of five years. Conviction as part of a “continuing criminal enterprise” triggered a 20-year mandatory-minimum. Conspiracy laws made all members of a drug operation legally liable for all the operation’s crimes: a youngster whom drug dealers paid a few dollars a day to act as a lookout, for instance, could be hit with the same stiff penalties as his bosses. In 1994 Congress introduced a “safety-valve”, which allowed judges to ignore mandatory minimums for certain non-violent informants, but its stringent terms disqualify most people convicted of drug-related offences. Drug offenders are nearly half of all federal prisoners, and most people convicted of federal drug offences received mandatory-minimum sentences. Since 1980 the federal prison population has soared from 24,000 to 219,000; between 1980 and 2013 the federal Bureau of Prisons budget rose by almost 600% in real terms. Federal prisons today house nearly 40% more inmates than they were designed for. Meanwhile, America’s violent-crime rate is less than one-third what it was in 1982, and less than half what it was in 1997. Some argue that prison works. The reason crime has fallen so sharply, they say, is that bad guys who are locked up cannot mug you. This is true, but America long ago passed the point where imprisoning more people is a cost-effective way of reducing crime. Bert Useem of Purdue University and Anne Morrison Piehl of Rutgers University find “accelerating declining marginal returns” to incarceration in America. In other words, locking up violent criminals while they are young, strong and reckless does indeed keep the streets safer, but keeping them locked up deep into their dotage costs a fortune and prevents very few crimes.

It is also unfair. Harsh, inflexible sentencing rules inflict punishments that no reasonable judge would impose. Jack Carpenter, for example, sold medical marijuana to dispensaries in California, where it is legal, but was still sentenced to ten years in prison by a federal judge. The high cost of mass incarceration has attracted attention from both left and right. In March Rand Paul, a Republican senator, and Patrick Leahy, a Democratic one, introduced the Justice Safety-Valve Act of 2013, which would let judges impose sentences below the mandatory minimum. In July Mr Leahy, along with Dick Durbin and Mike Lee, a Democrat from Illinois and a Republican from Utah, introduced the Smarter Sentencing Act of 2013. It would, among other things, shorten mandatory minimums and expand the safety-valve. And this week, in a speech before the American Bar Association, Mr Holder announced a clutch of reforms. More elderly federal inmates are to be released early. More effort will be made to help ex-convicts re-enter society, in the hope that this will curb re-offending. Pointless rules making it harder for ex-cons to find homes or jobs will be reconsidered. And most important, low-level, non-violent drug offenders without ties to gangs or cartels will no longer be charged with crimes that trigger mandatory minimums.

Texas won’t hold ’em

As Mr Holder noted, these policy shifts mirror similar ones that more than half of all American states have enacted over the past decade. The wave began with Texas—then as now led by Mr Perry—which in 2003 passed a law sending people convicted of possessing less than a gram of drugs to probation rather than prison. In 2007 Texas allocated $241m for drug-treatment and alternatives to prison for non-violent offenders. Between 2003 and 2011 violent crime in Texas fell by 14.2%. The state’s prison population has also declined steadily. Sentencing reform passed in Georgia—where one in 13 adults is imprisoned, on probation or on parole—will save the state an estimated $264m over the next five years. Kentucky’s is forecast to save the state $400m while reducing its prison population by 3,000 over the next ten years.

It is not clear how many sentences Mr Holder’s reforms will shorten or how much money they will save. Although the federal prison system is larger than that of any single state, it holds only 10% of American prisoners. Mr Holder has not changed any sentencing laws; he has ordered federal prosecutors to circumvent them. Some people object: Bob Goodlatte, the Republican chair of the House Judiciary Committee, chided Mr Holder for “selectively enforcing our laws and attempting to change them through executive fiat”.

Others say Mr Holder has simply exercised his prosecutorial discretion humanely. Molly Gill of Families Against Mandatory Minimums, a pressure group, says that after years of campaigning against discretion-free mandatory sentences, it feels at last as though her group is “pushing against an open door”. And “open door” is not a phrase you often hear in the same breath as “American prisons”.