Title of a superb story in the Wall Street Journal by Barry Latzer, who is also the author of an important book, The Rise and Fall of Violent Crime in America.

An excerpt.

It has become a boogeyman in public discourse: “mass incarceration.” Both left and right, from Hillary Clinton to Rand Paul, agree that it must be ended. But a close examination of the data shows that U.S. imprisonment has been driven largely by violent crime—and thus significantly reducing incarceration may be impossible.

Less than one-half of 1% of the U.S. population is incarcerated, according to the Bureau of Justice Statistics (BJS), so “mass” is a bit of hyperbole. The proportion of African-Americans in prison, 1.2%, is high compared with whites (0.25%), but not in absolute terms.

There’s a lot of historical amnesia about the cause of prison expansion, a mistaken sense that it was all about drugs or race and had very little to do with serious crime. This ignores the facts. Between 1960 and 1990, the rate of violent crime in the U.S. surged by over 350%, according to FBI data, the biggest sustained buildup in the country’s history.

One major reason was that as crime rose the criminal-justice system caved. Prison commitments fell, as did time served per conviction. For every 1,000 arrests for serious crimes in 1970, 170 defendants went to prison, compared with 261 defendants five years earlier. Murderers released in 1960 had served a median 4.3 years, which wasn’t long to begin with. By 1970 that figure had dropped to 3.5 years.

Unquestionably, in the last decades of the 20th century more defendants than ever were sentenced to prison. But this was a direct result of changes in policy to cope with the escalation in violent crime. In the 1980s, after well over a decade of soaring crime, state incarceration rates jumped 107%.

When crime began to drop in the mid-1990s, so did the rise in incarceration rates. From 2000 to 2010, they increased a negligible 0.65%, and since 2005 they have been declining steadily, except for a slight uptick in 2013. The estimated 1.5 million prisoners at year-end 2014 is the smallest total prison population in the U.S. since 2005.

Those who talk of “mass incarceration” often blame the stiff drug sentences enacted during the crack-cocaine era, the late 1980s and early ’90s. But what pushed up incarceration rates, beginning in the mid-1970s, was primarily violent crime, not drug offenses.

The percentage of state prisoners in for drug violations peaked at only 22% in 1990. Further, drug convictions “explain only about 20% of prison growth since 1980,” according to a 2012 article by Fordham law professor John Pfaff, published in the Harvard Journal on Legislation.

Relatively few prisoners today are locked up for drug offenses. At the end of 2013 the state prison population was about 1.3 million. Fifty-three percent were serving time for violent crimes such as murder, robbery, rape or aggravated assault, according to the BJS. Nineteen percent were in for property crimes such as burglary, car theft or fraud. Another 11% had been convicted of weapons offenses, drunken driving or other public-order violations.

That leaves about 16%, or 208,000 people, incarcerated for drug crimes. Of those, less than a quarter were in for mere possession. The rest were in for trafficking and other crimes. Critics of “mass incarceration” often point to the federal prisons, where half of inmates, or about 96,000 people, are drug offenders. But 99.5% of them are traffickers. The notion that prisons are filled with young pot smokers, harmless victims of aggressive prosecution, is patently false.

The other line of attack is that the criminal justice system is racist because blacks are disproportionately imprisoned. About 35% of all prisoners, state and federal, are African-American, while blacks comprise about 13% of the U.S. population. But any explanation of this disparity must take blacks’ higher rates of offending into account.

From 1976 to 1995, blacks were identified by police as the perpetrators in more than half of homicides, according to FBI data compiled by the BJS. During this same period, individuals interviewed for the national crime-victim survey described robbery perpetrators as black more than 60% of the time. While the rate of black violent crime fell dramatically after the mid-1990s, it remains disturbingly high. From 2000 to 2014, African-Americans were murdered eight times as often as whites per capita, nearly always as a result of black-on-black assaults.

Such serious crimes are still the main driver of African-American incarceration. The latest BJS figures, from the end of 2013, show that 57% of blacks in state prison were convicted of violent crimes. Only 16% were in for drug crimes. Those numbers nearly match the figures for the state prison population overall.