Crimes against people and property would be substantially higher today if the nation had not gotten tougher on criminals in recent years, according to a recent study by Steven D. Levitt published this May in The Quarterly Journal of Economics.

• The nationwide incarceration rate nearly tripled between 1973 and 1994, and the U.S. now imprisons seven times as many people relative to population as the average European country does.

• Violent crime would be about 70 percent higher today if our prison population had not increased since 1973 -- and property crimes would be about 50 percent more frequent.

• For each 1,000-inmate increase in the prison population, these annual reductions in crime will follow: four murders, 53 rapes, 1,200 assaults, 1,100 robberies, 2,600 burglaries, 9,200 larcenies and 700 auto thefts.

• On average, about 15 crimes per year are eliminated for each additional prisoner per year locked up.

And benefits far outweigh costs.

• The average criminal free to roam the streets does about $53,900 damage to society each year.

• The annual cost of incarceration is about $30,000 per prisoner.

• This yields an average net benefit of $23,900 per year for each criminal behind bars.

Source: Steve H. Hanke (Johns Hopkins University), "Incarceration is a Bargain," Wall Street Journal, September 23, 1996.

Several decades ago, Americans got fed up with soaring instances of crime and decided to do something about it. Having lost patience with theories of rehabilitation as jails became revolving doors for criminals, voters elected politicians who supported certain justice and longer sentences. The result was a huge surge in prison construction, followed, finally, by a dramatic drop in crime rates.

• As of 1997, 1.7 million offenders were in jail cells and off the streets.

• That amounts to a fourfold increase over the number incarcerated a quarter century ago.

• States' spending on prison systems has more than doubled over the past 10 years.

• Today, about one-fourth of state and federal prisoners are serving time for drug crimes -- compared to 9 percent in 1986.

Prison inmates are far more likely to be black men than their proportion in the general population would indicate. Some experts warn that in many black communities the stigma against going to prison has almost disappeared. "It's like going away to war," reports Geoffrey Canada, who works with impoverished youths in New York City's Harlem neighborhood. "Everyone gets called. You go. You do your time. It's no big thing," he says.

But blacks in poor neighborhoods are most often the victims of crime. "We have to send our children the message that crime is not going to pay," argues Richard Mosley, a former jail guard who works with young blacks in Baltimore. "Sending a message that this is not going to be tolerated is the one way to bring down these astronomical numbers of young black men in prison," he states.