This forum has featured repeated assertions that college has been oversold. In the latest issue of Barron’s, economist Bryan Caplan reviews a new book, Peter Cappelli’s Will College Pay Off?, that addresses the same topic.

Should you go to college? For 30 years, education economists have treated this decision as a no-brainer. B.A.s outearn high school grads by 75%. Assuming free tuition, that’s a real return of 15% a year: You give up four years of high school wages to earn college wages ever after. Tuition drags returns down, but not much. Economists’ confidence has proved infectious. They’ve convinced other social scientists, policy-makers, and politicians. Who are students—or parents—to demur?

Wharton School management professor Peter Cappelli’s Will College Pay Off? argues that the experts’ pro-college consensus is naive. Good advisors tailor advice to the client: “For every prescription drug, there is clear evidence that it has the desired effect, on average,” but your doctor “has to decide whether the benefits…are worth the potential side-effects…”

For one thing, college payoffs vary widely by major and school. According to PayScale data for 1,310 colleges, “Brigham Young and Georgia Tech both top the list with a 12.5% annual return, but there are many schools that generate a negative return.”

Good advisors are also upfront about the risk of failure. The returns to college are normally reported for graduates who finish on time. Yet such students are the exception, not the rule: “Less than 40 percent of full-time students entering four-year colleges in recent years have been graduating in four years.…For those who are sure that their kids will graduate in four years or else, I can say from personal experience that demanding that your kids will do so doesn’t guarantee that they will.”

A deeper methodological problem with the standard approach is that it gives college all the credit for the extra money that college grads enjoy. But on graduation day, the college-bound already outshine their classmates.

Caplan identifies major problems with Cappelli’s book — errors, omissions, implausibilities — but he concludes that “if you want to figure out what to do with your life — or help your child do the same — Cappelli tells you what you need to know.”