The WSJ reports today on the average lifetime earnings advantage conferred by a college degree. This statistic is probably worse than useless. “College” isn’t a single thing, and its benefits will not likely be enjoyed equally by every single student, even those pursuing precisely the same degrees.

For a college earnings premium figure to be of any value to policymakers or prospective college students, it would be necessary to break it down by field and by student characteristics. What’s the premium difference, for instance, between workers who majored in engineering, chemistry, computer science, mathematics, economics, etc., compared to those who majored in communications, art history, social work, multicultural studies, etc.? A similar breakdown of interest would be by SAT score.

These breakdowns would help people to make better informed decisions. An overall earnings premium estimate may well be worse than nothing: leading to great over- or underestimates for the value of a particular college degree to a particular student.