Success breeds failure. Policies and practices well suited to society at one juncture in history are often poorly suited to the world they have beneficially transformed. If you carry a good thing too far, it can turn out not to be a good thing anymore.

Case in point, one of the most successful public policies in U.S. history, the World War II G.I. Bill, which financed college educations for military veterans. Signed by former President Franklin Roosevelt, it embodied New Deal generosity even as its chief backers included the racist Democratic Mississippi Rep. John Rankin and the supposedly reactionary American Legion. One secret of its success, like that of Social Security, was apparent reciprocity: It provided benefits for those who made some contribution.

In doing so, it subsidized both economic and intellectual upward mobility for those from modest or even subsistence beginnings — the children of Appalachian coal miners, eastern and southern European immigrants, and even many Black Americans whose service was limited to segregated units.

Taken together, their achievements not only increased the enrollment of colleges and universities (many of which disliked the democratization) but vastly increased the size and capacities of the American economy.

This success embedded in the minds of elites and many ordinary Americans the notion that any further expansion of higher education would be good for individuals and the country. State legislatures founded new systems of universities and community colleges. Congress pumped large sums into higher education and took up the idea of somehow subsidizing loans to college and graduate students.

As a result, the share of Americans pursuing higher education rose from just 5% before WWII to nearly two-thirds today, with almost 40% earning a bachelor’s degree. Those numbers have been increased by seemingly generous student loans, the proceeds of which are gobbled up by a vast increase in higher education administrators (they now outnumber teachers) and by ever-higher tuitions.

As Charles Murray argued in his 2008 book “Real Education,” these are far higher percentages than the share of the population with the cognitive skills needed to profit from serious four-year undergraduate study, much less advanced graduate school. Schools have responded with reduced rigor and grade inflation to the point that, as Palantir CEO Alex Karp noted, “Inflated grades have degraded the value of college degrees.”

The result is that American society, which before the G.I. Bill tended to provide higher education to too few, now provides it to too many. Consequently, we have what the maverick scholar Peter Turchin called an “overproduction of elites.”