<p>Perhaps the rapid economic growth in the 1950s to 1970s had a lot to do with increasing the use of “human capital” through increased educational attainment by people who would not have been highly educated in earlier times (meaning their economic output was less than it would have been had they been able to attain higher education levels).</p>
<p>But now, it seems like we have already mostly “used up” that potential source of economic growth, since increasing college degree attainment from where we are now would be very difficult, given the state of K-12 education in the US. Better K-12 education would allow for increasing college degree attainment, but improving K-12 education overall seem to be very difficult in the US.</p>