From an article in the Boston Review:

According to a 2005 report of the International Centre for Prison Studies in London, the United States—with five percent of the world’s population—houses 25 percent of the world’s inmates. Our incarceration rate (714 per 100,000 residents) is almost 40 percent greater than those of our nearest competitors (the Bahamas, Belarus, and Russia). Other industrial democracies, even those with significant crime problems of their own, are much less punitive: our incarceration rate is 6.2 times that of Canada, 7.8 times that of France, and 12.3 times that of Japan. We have a corrections sector that employs more Americans than the combined work forces of General Motors, Ford, and Wal-Mart, the three largest corporate employers in the country, and we are spending some $200 billion annually on law enforcement and corrections at all levels of government, a fourfold increase (in constant dollars) over the past quarter century.

Never before has a supposedly free country denied basic liberty to so many of its citizens. In December 2006, some 2.25 million persons were being held in the nearly 5,000 prisons and jails that are scattered across America’s urban and rural landscapes. One third of inmates in state prisons are violent criminals, convicted of homicide, rape, or robbery. But the other two thirds consist mainly of property and drug offenders. Inmates are disproportionately drawn from the most disadvantaged parts of society. On average, state inmates have fewer than 11 years of schooling. They are also vastly disproportionately black and brown.

An interesting case in point is New York City. Analyzing arrests by residential neighborhood and police precinct, the criminologist Jeffrey Fagan and his colleagues Valerie West and Jan Holland found that incarceration was highest in the city’s poorest neighborhoods, though these were often not the neighborhoods in which crime rates were the highest. Moreover, they discovered a perverse effect of incarceration on crime: higher incarceration in a given neighborhood in one year seemed to predict higher crime rates in that same neighborhood one year later. This growth and persistence of incarceration over time, the authors concluded, was due primarily to the drug enforcement practices of police and to sentencing laws that require imprisonment for repeat felons. Police scrutiny was more intensive and less forgiving in high-incarceration neighborhoods, and parolees returning to such neighborhoods were more closely monitored. Thus, discretionary and spatially discriminatory police behavior led to a high and increasing rate of repeat prison admissions in the designated neighborhoods, even as crime rates fell.

Fagan, West, and Holland explain the effects of spatially concentrated urban anti-drug-law enforcement in the contemporary American metropolis. Buyers may come from any neighborhood and any social stratum. But the sellers—at least the ones who can be readily found hawking their wares on street corners and in public vestibules—come predominantly from the poorest, most non-white parts of the city. The police, with arrest quotas to meet, know precisely where to find them. The researchers conclude:

Incarceration begets more incarceration, and incarceration also begets more crime, which in turn invites more aggressive enforcement, which then re-supplies incarceration . . . three mechanisms . . . contribute to and reinforce incarceration in neighborhoods: the declining economic fortunes of former inmates and the effects on neighborhoods where they tend to reside, resource and relationship strains on families of prisoners that weaken the family’s ability to supervise children, and voter disenfranchisement that weakens the political economy of neighborhoods.

Its an interesting article. If you have the interest and the time, its worth a read.