Although there is clearly a correlation between earnings and a four-year degree, a correlation isn’t the same thing as a cause. Economists like Robert Reischauer ruffled feathers several years ago by pointing out that talented, driven kids are more likely to go to college in the first place — that they succeed, in other words, because of their innate abilities, not because of their formal education. Bill Gates, who dropped out of Harvard to start Microsoft, certainly doesn’t fit the stereotype of a low paid college dropout.

In fact, more than a couple of billionaires never graduated from college. Larry Ellison, cofounder of database giant Oracle, dropped out of the University of Illinois and is now worth $16 billion. Fellow billionaire John Simplot, inventor of the frozen French fry, never even finished high school. Neither did Alan Gerry, who built the first cable television network in upstate New York and then sold it to Time Warner Cable for $2.8 billion.

In fact, there is plenty of evidence that what really matters is how smart you are, not where — or even if — you went to school. According to a number of studies, small differences in SAT scores, which you take before going to college, correlate with measurably higher incomes. And, according to a report from the National Bureau of Economic Research, the lifetime income of high-school dropouts is directly associated with their scores on a battery of intelligence tests.

By this logic, the real economic value in a Princeton degree is not the vaunted Princeton education, but in signaling potential employers that you are smart enough to get into Princeton. Actually, attending the classes is irrelevant. [Should the comma be there? Sentence makes sense either way, I guess, but reads better without.] A few years back, we even went so far as to speculate that an entrepreneur could build a healthy businesses by charging, say $16,000, to certify qualified high-school graduates as Ivy League material. (See: “Is Yale A Waste Of Money?” ) College-skippers could invest the $144,000 savings and have a nice nest-egg built up by the time they are in their mid-30s. And they could use their formative years between 18 and 22 to learn an actual trade.

For, in truth, most professions — journalism, software engineering, sales, and trading stocks to name but a few — depend far more on “on-the-job” education than on classroom learning. Until relatively recently, lawyers, architects and pharmacists learned their trade through apprenticeship, not through higher education.

Certainly some jobs — medical doctors and university professors — require formal education. But many do not, and between the Internet and an excellent public library system, most Americans can learn pretty much anything for a nominal fee. By all means, go to college if you want the “university experience,” but don’t spend all that cash just on the assumption that it will lead you to a higher-paying job.