America’s criminal justice system is going to make history this week when the number of incarcerated people surpasses two million for the first time. But this is a development for which neither political party will attempt to claim “credit.” Indeed, people across the political spectrum seem to recognize that this is a sad occasion–an occasion that raises a nagging question: Why do so many Americans need to be kept behind iron bars?

To fully appreciate why this is such an extraordinary moment, one needs to put the two-million-prisoner factoid into historical context. As the nearby chart shows, it took over two hundred years for America to hold one million prisoners all at once. And yet we have managed to incarcerate the second million in only the last ten years. Analysts at the Justice Policy Institute point out that our per-capita incarceration rate is now second only to Russia’s. This is hardly something that anyone would proudly tout as an “achievement.”

Estimated Prison Population in the U.S. 1930 - 2000

Throughout the 1990s, billions of dollars were spent on prison construction. But the supply of space did not stay ahead of demand. As soon as prisons were built they were immediately filled with prisoners. In fact, most prison facilities are presently operating beyond their design capacity.

The massive expenditure of tax dollars on prison construction has spawned some bizarre dynamics. A generation ago, few people wished to live near a prison. Today, small towns and cities undergoing hard times tenaciously lobby for prisons to be built in their backyards. Those cities that are unsuccessful go back to the state legislature to push for more prison construction–and then vie again for the coveted selection site.

In California, the Correctional Peace Officers Union has grown so large that it is now a political force. With over 27,000 dues-paying prison guards, the union gives political contributions to the candidates who promise to build more prisons, hire more guards, and increase guard salaries and benefits. And the private firms who contract with the prison authorities for assorted supplies are political players too–since they are well aware that as the prison population grows, their revenues rise ever higher. Some analysts have dubbed this political racket the “prison-industrial complex.”

Proponents of incarceration tend to brush off these disturbing side-effects. They tell us that when our incarceration rate is low, our crime rate is high–and that the declining crime rates that we have witnessed in recent years are the result of tough, no nonsense incarceration policies. While it is regrettable that we are now locking up millions of people, they say we have a simple choice: more prisons or more crime.

On closer inspection, the choice is not so stark. The first thing to clarify is what we mean by “crime.” For as Stanford law professor Herbert Packer once noted, “We can have as much or as little crime as we please, depending on what we choose to count as criminal.”

No one can dispute that prison cells incapacitate convicts. A serial rapist, for example, cannot prey upon his old neighborhood while he is behind barbed wire fences. On the other hand, there is no corresponding increase in public safety when government incarcerates a person for using or even selling drugs. Years of experience show that drugs are not rendered less available by locking up drug offenders. The law of supply and demand states that as long as there is a demand for a product, the market will make that product available at some price. A “black” market operates under the same law.

A close look at crime statistics reveals that the drug war is fueling the remarkable growth in our prison population. In 1981, only 22 percent of federal inmates were drug prisoners. Today, 60 percent are drug prisoners.

One nasty (but unavoidable) effect of waging a drug war with limited jail space is that violent criminals will sometimes be released from prison in order to make room for drug offenders. That “displacement effect” can be addressed in one of two ways. We can end the drug war–or we can build more prisons. It might make sense to build more prisons if we were about to capture the last few hundred remaining drug dealers and users. But since we are nowhere near that point, it is not good policy to put more money into prison construction. Indeed, the government itself estimates the number of American drug users to be in the millions.

Because policymakers have refused to come to grips with the discordant effects of a failed drug policy, we should declare a moratorium on new prison construction until the drug war is ended. Limited prison capacity is one of the only things restraining the politicians from escalating a futile crusade to even higher levels.