In Chicago, a police crackdown on open-air drug markets has helped the city's murder rate drop to a 33-year low.
In Baltimore, a focus on crime "hot spots" has contributed to a similar reduction in homicides.
But in Boston, the level of crime rose in almost every category for the first six months of 2000 - with the number of murders climbing 50 percent, from 16 to 24.
As the nation starts a new year, violent crime resembles a complicated mosaic.
Overall, after dropping dramatically for the past eight years, reports from around the country indicate the crime rate is continuing to decrease, although modestly.
But in some cities, the numbers are edging upward again, foreshadowing what some criminologists say is an omen for the start of a new century.
Some of the increases are perhaps inevitable. Rates had dropped so low in many cities in the 1990s that they had nowhere to go but up - a phenomenon one expert calls the "criminal-justice limbo stick." "Cities had great success in bringing the crime rate to a very low level," says James Alan Fox, a criminologist at Northeastern University in Boston. "Now the difficulty is maintaining it."
Many factors are credited with the almost decade-long drop in violence on America's streets. They include the flourishing economy, the implementation of innovative police tactics, the aging of the baby boomers, and tougher crime laws.
Some criminologists believe that many of these factors have reached a peak, squeezing as much illegal activity out of the system as possible.
Others are more sanguine, noting that lessons learned during the past decade are continuing to be applied in innovative ways around the country.
"We weren't very good at predicting the decrease," says Margaret Zahn, a criminologist at North Carolina State University in Raleigh. "We're not going to be real good at predicting the increase either."
A spotcheck of cities across the US shows reports are mixed:
* In Minneapolis, a crime-prevention strategy based on "rapid deployment and relentless follow-up and assessment" implemented in 1998 has brought violent crime down 33 percent.
* Baltimore's increased focus on high-crime hot spots and the creation of a fugitive task force have helped bring the city's murder rate down to 262, the first time it's dipped below 300 in recent memory.
* The overall crime rate continued to decrease in New York, dropping more than 5 percent last year. But the number of murders was up by four, to 671. That's still near the 30-year low, but many experts see the up-tick as a sign those strategies need some reworking.
The city pioneered some of the more aggressive, proactive crime fighting techniques of the 1990s.
"That kind of aggressive policing has led to highly publicized incidences of abuse, along with racial profiling," says Roger Lane, a crime expert at Haverford College in Pennsylvania. "Even the cops in New York say it's time to ease up some."
Then there's the slowing economy. That could impact employment opportunities for teenagers, as well as local budgets. During the economic recessions of the 1980s, cities like Philadelphia cut their recreational budgets along with their police forces. The end result, their crime rates soared.
That's a lesson they might keep in mind if the economy goes sour again. "It's a question of how we choose to use our resources," says Charles Friel, a professor at Sam Houston State University in Texas.
Another variable is how the nation responds to its growing teenage population, which is about to hit its peak crime-committing years. The biggest hike is among African-Americans and Hispanics, where the rate of offending is higher, as well as the rates of victimization.
"We will have more kids at risk, and that has the potential to translate into more youth violence," says Professor Fox. "I'm not saying we're going to have another crime wave, but the potential is there."
But Fox and others note the overall population is still aging, so overall crime rates may continue to inch downward, with a spike only in the juvenile crime rate.
Another factor which led to the 1990s drop in the crime rate is what Professor Friel calls the nation's "get tough and lock 'em up" philosophy which has led to a record number of people being sent to prison. "We've taken an increasing number of classical criminals, that tend to be high-rate offenders, out of circulation for a couple of years," he says. "That takes that much crime out of the system."
But when you send record numbers of people to prison, record numbers will eventually come out. That process has already started. Gang members sent away 10 years ago are being released in cities like Boston and Los Angeles. And because of the shift away from rehabilitation and education, many experts fear they'll have a hard time integrating back into the community.
"Rather than looking for a paycheck when they get out, many are looking for payback," says Fox. "If prisons aren't schools for crimes, they're at least study halls."
But even if the crime rate does start to inch up nationwide, Fox insists there's no need to panic. The country is still far safer today than it was 10 years ago.
"I call that the Mark McGwire effect. When Mark McGwire doesn't hit 70 home runs, that doesn't mean he's washed up," says Fox. "I think we need to look at the long-term trends."
(c) Copyright 2001. The Christian Science Publishing Society