Inside Higher Ed features a terrific essay today by economist Michael Rizzo. Rizzo takes issue with President Obama’s goals to have all Americans complete at least one post-secondary year of education or job training, and for the nation to have the world’s highest percentage of college graduates by 2020. I’ve opined about this before, but Rizzo does it much more comprehensively, noting especially that — surprise! — education can suffer from “diminishing returns.”

Here’s the meat of Rizzo’s piece, but you really should read the whole thing:

More education has to be a good thing. After all, receiving more schooling can’t make you less productive, right? Education is like exercise, reading, spending time with one’s children, and sleeping – each of these is good for you. It is obvious that dedicating more attention to each of these is good. It is obvious … and wrong – for both individuals and societies as a whole.

While investing in each of these likely generates enormous benefits when starting from scratch, at some point each additional unit invested generates fewer benefits than the one before it – just as eating that fourth doughnut brings you less satisfaction than did the second. What if these so-called “diminishing returns” never set in for education? In a world of scarce time and resources, they must, albeit indirectly. Dedicating more resources to the production of educated workers must come at the expense of resources dedicated to creating other important capital goods, institutions, or consumption goods. An individual cannot dedicate 24 hours in a day to everything, nor can society dedicate all of its resources to everything. Put another way, if merely leading the world in educational attainment is desirable, why not aim to have every American receive a college degree? Better yet, why not aim to have every American earn a Ph.D.?