AMITY SHLAES: American history shows that expanding the economy benefits everyone.

Decades in which policy endeavored or managed to even out and equalize earnings—the 1930s under Franklin Roosevelt, the 1960s under Lyndon Johnson—score high. Decades where policymakers focused on growth before equality, such as the 1920s, fare poorly. Decades about which social-justice advocates aren’t sure what to say—the 1970s, say—simply drop from the discussion. In the same hierarchy, federal debt moves down as a concern because austerity to reduce debt could hinder redistribution. Lately, advocates of economically progressive history have made taking any position other than theirs a dangerous practice. Academic culture longs to topple the idols of markets, just as it longs to topple statutes of Robert E. Lee.

But progressives have their metrics wrong and their story backward. The geeky Gini metric fails to capture the American economic dynamic: in our country, innovative bursts lead to great wealth, which then moves to the rest of the population. Equality campaigns don’t lead automatically to prosperity; instead, prosperity leads to a higher standard of living and, eventually, in democracies, to greater equality. The late Simon Kuznets, who posited that societies that grow economically eventually become more equal, was right: growth cannot be assumed. Prioritizing equality over markets and growth hurts markets and growth and, most important, the low earners for whom social-justice advocates claim to fight. Government debt matters as well. Those who ring the equality theme so loudly deprive their own constituents, whose goals are usually much more concrete: educational opportunity, homes, better electronics, and, most of all, jobs. Translated into policy, the equality impulse takes our future hostage.

Touring American history with an eye on growth, not equality, has become so unusual that doing so almost feels like driving on the wrong side of the road.

The Left gave up on “A rising tide lifts all boats” a long time ago.