from James Taranto’s interview with Bryan Caplan:
"Research comparing the personal and the national payoffs of schooling finds a wide discrepancy—in 'the ballpark of, if a year of school for an individual raises earnings about 10%, [then] if you go and raise the education of an entire country’s workforce by a year, it seems to only raise the income of the country by about 2%.'
"Mr. Caplan therefore reckons that roughly 80% of the education premium comes from signaling, only 20% from marketable skills."
Source: “
The Weekend Interview,” WSJ, 4/14/2018