It’s good to see President Obama and members of Congress take an interest in criminal justice reform, but their emphasis is wide of the mark. The problem is not, as is so often said, that the system is “broken.” To the contrary, the criminal justice system is arguably the most successful domestic program in the last 50 years.

Today, we have more than 5 million fewer serious crimes in this country per year than we did a generation ago. We have 10,000 fewer murders. The crime rate is half what it was in the early ’90s, at levels not seen since the Baby Boomers were in grade school.

Would that all our domestic programs were this “broken.”

Our huge success in cutting back on crime did not fall out of the sky. It results from many factors — more police, more proactive policing, and the aging of the most crime-prone segment of the population, for example — but more serious sentencing and greater use of incarceration are major contributors. The eminent criminologist Professor James Q. Wilson concluded that 25 percent or more of the drop in crime is due to increased imprisonment, and other authorities have reached the same figure.

It may sound appealing to say that we should become more forgiving, should eliminate sentencing rules for judges (such as mandatory minimum statutes), and have greater faith in rehabilitation. The problem is that we’ve tried these things before, for at least a quarter century in the ’60, ’70s and part of the ’80s. For our trouble, we got a national crime wave.

Instead of the dramatically falling crime we have today, crime skyrocketed in those years by more than 300 percent. Whole cities became free-fire zones with the gunplay common to drug dealing. The country had 450 murders a week. What now goes by the name “sentencing reform” is nothing more than an invitation to return to the disastrously failed policies of the past.

It is true, as many have noted, that our system sometimes makes mistakes, as every human system does. There are some wrongful convictions and sentences (as well as, of course, mistaken acquittals).

But contrary to what sentencing reform advocates would have us believe, people do not wind up incarcerated because the system makes bad choices. They wind up incarcerated because they make bad choices. The truth is that the great majority of inmates serving long terms are there because of repeat, serious offenses. This is scarcely an argument to start cutting back on sentencing laws that have averted so much misery and saved so much loss for so many innocent people.

What will happen if we start to cut back on incarceration?

We’re already starting to find out. As the rate of imprisonment has begun to flatten over the last few years, troubling signs are on the horizon. The Justice Department has warned that we are in the throes of a heroin epidemic. Just in the last year, in cities from coast to coast, the murder rate spiked. Even as things stand, the recidivism rate — the frequency with which released inmates return to crime — is a startling 77 percent. Is this the time to signal retreat? To cut back on a crime-fighting tool we know works? To tell criminals that THEY are not the problem, that WE are the problem?

Finally, we shouldn’t be fooled by the notion that “sentencing reform” will be limited to low-level, non-violent offenders, although it’s often advertised that way. Some of the leading pro-reform organizations, such as Families Against Mandatory Minimums, have made it clear that violent offenders also should be included in the windfall.

But even beyond that, we shouldn’t be lulled by the talk of “non-violent” offenses, even if reform were so limited. The telling question for sentencing purposes is not just whether the offense involves violence; it’s whether it involves HARM.

Non-violent offenses do incalculable harm. The trafficking and consumption of hard drugs, for example, is one of the most socially destructive enterprises going on in America, even when if comes without direct violence.

There’s nothing violent going on when a teenage addict slides the needle in his arm, but if he gets the dose wrong, he’ll be dead by nightfall.

There’s nothing violent going on when a 9-year-old is enticed to pose for obscene pictures, but her childhood has been poisoned.

There’s nothing violent going on when an older couple is swindled out of their life savings, but their hopes for the future are gone.

The siren song of the “low-level, non-violent” offender will lead us back to bad old days of the ’60s and ’70s, in which the people least able to defend themselves — children, the elderly, the poor, the addicted and minorities — will be hurt the most.

But make no mistake, we will be hurt. Our system may look broken to the mugger, the meth dealer or the swindler serving a long sentence he went out of this way to earn, for the rest of us — the 99.3 percent who are not in prison — it’s a system to preserve, not dismantle.