I always tell the students in my crime and criminal justice class that they should never leave Maine. Maine is such a great state that no one should want to leave it, of course, but my tongue-in-cheek advice has more to do with crime rates than with Maine’s many virtues.

First of all, Maine has one of the lowest crime rates in the nation, along with states such as New Hampshire, Vermont, North Dakota and South Dakota. This is probably because all these states are cold and rural, but that’s a story for another day.

Second, one of the many little secrets of the U.S. criminal justice system is that very few people go to prison compared to the number of felonies in a given year. This is not because we have a lenient system or because criminal justice professionals are slacking on the job. It’s simply a matter of numbers: Many crimes are committed, fewer are reported to the police, and fewer still lead to arrest, conviction and imprisonment.

The decrease that occurs at all stages of the process represents a funnel, with many crimes going into the top of the funnel and only a few incarcerations coming out of the bottom. Let’s examine the stages of this criminal justice system funnel.

In 2006, the latest year for which full data is available, about 21.4 million felonies (homicide, rape and sexual assault, robbery, aggravated assault, burglary, larceny, motor vehicle theft) occurred, according to the National Crime Victimization Survey and other federal sources. Because many people do not report their victimizations to the police, the number of crimes known to the police that year was only about 11.4 million.

Despite what TV crime shows might suggest, it is practically very difficult for the police to arrest most suspects, so only about 2.2 million felony arrests occurred. Many of these cases were dismissed for lack of evidence, and others were reduced by plea bargaining to misdemeanor charges. As a result, the number of felony convictions in 2006 was only about 436,000. In turn, about 321,000 of these convictions led to incarceration.

So, 21.4 million felonies led to 321,000 incarcerations. If we do some math, we see that the number of incarcerations was only about 1.5 percent of the number of felonies. Turning that last number around, about 98.5 percent of felonies do not result in incarceration in a given year.

Even if we assumed that each incarcerated offender might have committed 10 felonies that year (about the maximum that criminologists estimate for this number), then the incarcerations still would have accounted for only 15 percent of all felonies.

To repeat, this funnel is not the result of a lenient criminal justice system, as the United States has the harshest system of all the world’s democracies. Nor is it the result of inept policing, prosecuting and judging. It is simply a matter of practical reality: Many crimes occur, many citizens do not report their crimes, and the police simply cannot find most suspects in real life as opposed to TV life and cannot gather sufficient evidence for conviction.

What should we do? It makes little sense to increase the number of incarcerations coming out of the bottom of the funnel. Even if we could do so, a questionable proposition, this would mean building more prisons to house the new inmates and then maintaining these prisons.

For example, even if we were able to double the 1.5 percent of all crimes coming out of the bottom of the funnel, we would eventually have to double our number of prisons, which are filled beyond capacity. To accomplish this goal would cost about $150 billion in prison construction costs and another $50 billion annually to house the new inmates. Even with this huge expenditure, most crimes would still not result in incarceration, and we would hardly be any safer.

Rather than focus on the bottom of the funnel, then, it makes more sense to focus on the top of the funnel by trying to reduce the number of crimes occurring in the first place. This means putting more money into programs that address poverty, inadequate parenting and other social causes of crime. Crime prevention strategies such as this are far more cost-effective than incarceration in reducing crime.

In the meantime, until the United States devotes more attention to crime prevention strategies, and maybe even after it might do so, the message my students hear is one that we should all listen to: Never leave the state of Maine!

Steven E. Barkan is professor of sociology at the University of Maine and former president of the Society for the Study of Social Problems. He is a member of the Maine chapter of the national Scholars Strategy Network, which brings together scholars across the country to address public challenges and their policy implications. Members’ columns appear in the BDN every other week.