How do we measure the value of a degree to society?

I enjoyed this blog post from “Gas stations without pumps,” where he talks about how we value the “private good” value of a college education. But given the interesting distinction he makes in the first paragraph (below), I wonder if we could measure the value of a degree to a society, rather than to a person. How much good does it do the society and the economy for someone to earn their college degree? I’ve read evidence that dropouts have a high cost to society, but I don’t know how to measure the value that society gets by having someone finish. It’s an important question, as the cost of higher education gets increasingly shifted to the individual.

The ongoing privatization of higher education in the USA is driven largely by a view of education as a private good (of benefit primarily to the one receiving the education) rather than a public good (where society as a whole reaps the benefit of an educated populace). To make the “private good” view work, one has to convince people that there is a substantial benefit to the recipients of the education that far exceeds any benefit to society. This has generally been done in crassly monetary terms, talking about the earnings of graduates compared to those with less education (generally in lifetime earning terms, to make the differences appear as large as possible). By using a purely monetary assessment, one can conveniently ignore all the other effects on society, and pretend that education is purely a private investment in increasing earning potential.

via How much is a degree worth? « Gas station without pumps.