Some public-policy debates seem perpetual. And tragic, sensational events just last week may help explain why some disputes are so hard to settle, no matter how extensive evidence becomes on one side or the other.

Impassioned by the suffering involved in the social problems being debated, partisans on either side of stubborn policy quarrels often become deeply invested, personally and philosophically, in their predictions of what would follow if their misguided opponents’ ideas were adopted. They quickly seize on evidence that appears to confirm their expectations, but find it challenging to see broader indications that their prediction may have been wrong.

Yet occasionally it happens that what social scientists call a “natural experiment” unfolds — often when one side in a long-running disagreement manages to enact its controversial policy prescription, at least in some jurisdictions. Over time, this allows us to test predictions — with data, not anecdotes ­— ­against reality.

Two notable natural experiments of this kind are in the news — one because its results seem increasingly clear, and the other because it is just getting underway.

The experiment whose results seem increasingly clear has been the coast-to-coast liberalizing of gun permit laws over the past several decades. An appalling on-air murder of a TV news crew in Virginia last week has of course reignited the broad debate over gun violence in America, as have so many shocking individual incidents before it. But the bigger picture, at least where carry permits are concerned, is less confounding and disturbing.

Only last Sunday, a front-page Star Tribune news story reported that 200,000 Minnesotans now hold legal permits to carry handguns — far more than were forecast by the most alarmed opponents of relaxed permit laws back in 2003, when the proposal to allow essentially any law-abiding adult to carry a handgun was enacted.

And yet, the paper reported, “Bureau of Criminal Apprehension data show that fatalities involving permit holders are rare,” defying the fears of “opponents … that the law would lead to a surge in shootings and gun deaths.”

Those fears were often vividly expressed. A Star Tribune editorial in 2003, citing a Brookings Institution study, warned that “when average citizens regularly have guns in pockets or purses … , ‘[o]therwise law-abiding people may become emboldened to do bad things, some of them violent.’ ”

There’s little evidence that this “average citizen” violence has come to pass in any widespread way, although advocates continue to cite scary-sounding numbers. Last Sunday’s analysis dutifully noted reports of at least 568 fatal shootings by permit holders across the country — since 2007.

But with some 13 million permit holders now in America, that seven-year total represents a fraction of the homicide rate among the general population.

Of course, it also should be noted that little evidence confirms the lavish predictions of gun-rights advocates that crime would plummet as a result of proliferating permits. Crime has indeed dropped, not risen, and last Sunday’s story documented two recent local cases of self-defense by permit holders. But the causes of the long-term general decline in crime are many.

Meanwhile, of course, larger controversies about gun policy in America remain — especially over gaps in laws and enforcement that make it possible for firearms to be purchased by disturbed and dangerous people, including some who might never be issued a carry permit even under today’s liberalized rules. Virginia, meanwhile, is among a significant number of “open carry” states where weapons can be openly carried without a permit.

Still, easier gun permitting has not been responsible for unleashing a nightmare of average citizen violence in America.

Another set of dire predictions that may soon be tested by new evidence concerns the minimum wage — predictions that compelling higher pay for low-skill workers inevitably destroys jobs.

Economists have differed on this question for years, with a rough middle-of-the-road consensus forming around the idea that modest increases in the minimum wage do little harm to employment levels (instead correcting for an information and power imbalance between employers and low-wage workers). But big minimum-wage increases are widely thought to be riskier.

Many cities and states (including Minnesota) have enacted “modest” minimum-wage hikes in recent years. But over the last year, progressives in places like Los Angeles, New York, Seattle and more have pushed through striking rises to $15 an hour and beyond. Minneapolis leaders have talked about following suit.

These whopping minimum-wage hikes, whatever else they accomplish, should provide impressive natural experiments on the effect of bold interventions in the labor market. The results will be worth watching, especially for communities pondering a similar course.

Economic analysts can hardly wait, it seems, to see if predictions of economic mayhem from higher wage floors fare better than predictions of chaos among permit holders did.

While admitting it’s very early, David Ozimek of Moody’s Analytics recently wrote on his Dismal Scientist blog of “Troubling Signs of Minimum Wage Damage in Los Angeles.”

Ozimek reports that accommodations employment started falling in Los Angeles last fall, almost as soon as the city approved a big, phased-in minimum-wage increase for hotel workers. By this June — still before the wage hike actually took effect — employment in the sector was already down 4.8 percent.

Ozimek is at pains to acknowledge that the data are merely “suggestive” at this point. But what the numbers suggest, he adds, “should worry those who have been less concerned about big minimum wage hikes.”

One particular cause of concern might be that, as a political matter, lofty minimum wages may not be an easy policy to reverse if they turn out to do more harm than good. Policy­makers here in Minnesota might be well-advised to wait and see how things turn out.

But candidly, this minimum-wage experiment ought to be causing more than one kind of anxiety. If it turns out that even sharply higher minimum wages don’t shrink low-skill employment in some significant way, those of us who tend toward a classical free-market view of the economy will have some explaining — or, better, learning — to do.

There is no truer wisdom than the willingness to be proven wrong.


D.J. Tice is at