“Build it, and they’ll fill it.”

So say the opponents of the proposed Johnson County justice center, a proposed jail-and-courtroom complex that the county says would ease overcrowding in their current facilities.

Back in November, the first justice-center proposal failed to charm the voters. Too expensive, they said. Too likely to be filled.

A very modestly scaled-down plan will be brought to a vote on Tuesday. Its opponents are out again, in the streets, online, chirping:

“Build it, and they’ll fill it.”

For a long time, I thought this was a cynical way to look at this issue. It implies that but for a lack of beds in the county jail, police would menace the streets like rabid dogs, and judges would smite every petty offender seen groveling before the bench.

But if they build the justice center … well, something will happen. History and common sense tell us that they will, in fact, fill it with criminals.

The trends point toward larger and larger future inmate populations.

Between 1983 and 2011, the population of Johnson County increased by 154 percent. During that same 28-year period, the average daily population of the jail increased by 552 percent, according to a study from University of Iowa professor emeritus John Neff.

The county’s inmate wave coincided with the nationwide prison boom of the past three decades. In 1983, 275 of every 100,000 Americans were incarcerated, according Harvard sociologist Bruce Western’s book Punishment and Inequality in America. That number nearly tripled by 2009, when 743 of 100,000 Americans were locked up, statistics from the International Centre for Prison Studies show.

Today, United States’ incarceration rate exceeds those of the Western European states, typically by a factor of seven. Russia (that shining city on the hill) comes the closest to equaling America’s prison supremacy; 628 of every 100,000 Russians were imprisoned in 2008, according to the United Nations Office on Drugs and Crime.

In the United States, jails and prisons get filled to maximum capacity and then filled some more. Johnson County ships its extra inmates to nearby rural jails. Iowa Department of Corrections statistics show state prisons hold about 1,000 too many.

Given the history, the proper response to “If you build it, they’ll fill it” isn’t to shrug it off as the musing of a conspiracy nut, but to ask “why?”

Why have jail populations risen so steeply? If we get a bigger jail, why must we expect Johnson County law enforcement to fill it up?

The short answer is “they have to.”

It’s important to understand that the incarceration boom was not caused by rising crime. During the past few decades, prison populations expanded exponentially as crime rates fell.

This national trend held up locally, as well.

Between 1998 and 2009, the Johnson County Jail population increased by 178 percent while local arrest rates were unchanged, according to Neff’s study.

U.S. Department of Justice data indicate the violent crime rate in Iowa City didn’t change significantly between 1985 and 2010, though the property crime rate shrunk by half over the same period.

Western’s book concluded that rising incarceration rates are not related to crime trends but to changes to the criminal-justice system that emphasized incarceration and led to harsher jail sentences, particularly for low-level drug offenders.

During the 1980s and ’90s, Western argues, “tough-on-crime” conservative legislators led many states to adopt strict new laws. Limitations on parole, three-strikes laws, truth-in-sentencing laws, and mandatory minimum sentencing — punitive measures that were sold as weapons to aid the fight against drug crime — all metastasized during this period.

These laws changed the goal of American criminal justice from rehabilitation to incapacitation by imprisonment. Judges were allowed less discretion in sentencing; prisoners were locked up more liberally.

The legacy of punitive, incarceration-based laws can be seen at every level of the criminal-justice system.

Statewide, mandatory minimum sentencing has extended the average prison stay of drug offenders by 9.5 months, according to the Iowa Department of Human Rights and the state’s Division of Criminal and Juvenile Justice Planning. That contributes to overcrowding and high incarceration costs.

Locally, we’ve seen massive racial disparities in our jail, absurd incarceration costs.

Overcrowding.

Will a new jail solve these problems?

I’ve written often about the justice center, and I’m not sure I have the answer to that question. But I do know that this debate largely overlooks those truly responsible for the deplorable state of the criminal-justice system.

It’s not the police, nor the judges, though neither group is without fault.

It’s the Reagan-era conservatives and their modern descendants whose quixotic war on crime and drugs transformed the American prison system into a bloated warehouse for two-bit drug offenders.

They dismantled the rehabilitative criminal-justice system and built in its place a punitive Colossus founded on the false virtue of throwing away the key. Now we’re stuck debating how to patch up their disastrously flawed behemoth.

“Build it, and they’ll fill it?” Not exactly.

Build it, and they’ll have to fill it.