Some states and cities have already taken this matter into their own hands, setting their own minimum wages above the federal level to account for price and wage differences. (They have also done this because the federal minimum wage has become a political football that is often fumbled.)

At the current $7.25, the minimum wage is too low pretty much anywhere to provide working families much of an income (and, as I explain here, adults increasingly depend on the minimum wage to make ends meet). This year, 22 states have their own minimums, ranging from $7.40 in Michigan to $9.32 in the state of Washington. Seattle just agreed to take its minimum up to $15 on hour, though with a phase-in period of quite a few years.

Mr. Dube suggests two ways to set the minimum wage to account for this price and wage variation. One, set the minimum at half the state median wage. Why half? Why median? While any such choice would have an element of arbitrariness to it, in the 1960s and 1970s, when policy makers regularly attended to the national minimum wage, its average relative to the median was 48 percent. That’s one reason economic inequality didn’t grow much in those years. Internationally, the average minimum-to-median among countries tracked by the O.E.C.D. is also about 50 percent. “In contrast,” Mr. Dube writes, “the U.S. minimum wage now stands at 38 percent of the median wage, the third-lowest among O.E.C.D. countries after Estonia and the Czech Republic.”

How does this idea relate to R.P.P.s? As I noted, the correlation between state-level wages and prices is high, so benchmarking a state’s minimum wage to its median is one way to account for regional price differences.

But a more direct way is to simply take half the national median, $9.75 in 2014, according to Mr. Dube, and adjust it for R.P.P.s.

Since median wages vary a lot more than prices across states, I tend to think that this recommends the R.P.P. To me, it’s (slightly) more attractive to adjust minimum wages for price differences/buying power than for relative wages.

But there’s a larger point here. Economists endlessly and fruitlessly argue about whether the impact of minimum wages on jobs is very small or zero. Policy makers who most resist minimum wage increases tend to be ones representing the interests of states with lower prices and wages. To their credit, many states and even some cities are ignoring this unhelpful debate and taking action to raise the pay of their low-wage work force, push back a bit on inequality, and work around Washington’s dysfunction. If adjustments for local wages and prices makes this go down easier, so much the better.