Neil Irwin:

In their simulation, they assume that 10 percent of non-college-educated men of prime working age suddenly obtained a college degree or higher, which would be an unprecedented rise in the proportion of the work force with advanced education.

They assume that these more educated men go from their current pay levels to pay that is in line with current college graduates, minus an adjustment for the fact that more college grads in the work force could depress their wages a bit.

There is no doubt that in this simulated world with a more educated labor force, middle-income workers earn more — $37,060 in simulated 2013 earnings for a person at the 50th percentile, compared with $34,000 in the real world, a 9 percent improvement.