If you enjoyed reading the recent transcript of a Carolina Journal Radio interview with Ohio University economist Richard Vedder, discussing the government’s role in promoting a higher education “arms race,” you might appreciate a Wall Street Journal column Vedder has co-written this week with OU student Christopher Denhart.

[T]otal college enrollment has fallen by 1.5% since 2012. What’s causing the decline? While changing demographics—specifically, a birth dearth in the mid-1990s—accounts for some of the shift, robust foreign enrollment offsets that lack. The answer is simple: The benefits of a degree are declining while costs rise.

A key measure of the benefits of a degree is the college graduate’s earning potential—and on this score, their advantage over high-school graduates is deteriorating. Since 2006, the gap between what the median college graduate earned compared with the median high-school graduate has narrowed by $1,387 for men over 25 working full time, a 5% fall. Women in the same category have fared worse, losing 7% of their income advantage ($1,496).

A college degree’s declining value is even more pronounced for younger Americans. According to data collected by the College Board, for those in the 25-34 age range the differential between college graduate and high school graduate earnings fell 11% for men, to $18,303 from $20,623. The decline for women was an extraordinary 19.7%, to $14,868 from $18,525.

Meanwhile, the cost of college has increased 16.5% in 2012 dollars since 2006, according to the Bureau of Labor Statistics’ higher education tuition-fee index. Aggressive tuition discounting from universities has mitigated the hike, but not enough to offset the clear inflation-adjusted increase. Even worse, the lousy economy has caused household income levels to fall, limiting a family’s ability to finance a degree.

This phenomenon leads to underemployment. A study I conducted with my colleague Jonathan Robe, the 2013 Center for College Affordability and Productivity report, found explosive growth in the number of college graduates taking relatively unskilled jobs. We now have more college graduates working in retail than soldiers in the U.S. Army, and more janitors with bachelor’s degrees than chemists. In 1970, less than 1% of taxi drivers had college degrees. Four decades later, more than 15% do.