In the past having a university degree was an impressive achievement.  There are two reasons for this: 1) university educated people were less common, and 2) the correlation between IQ and years of education was much higher.

In the 1950s, the correlation between Wechsler global IQ and years of education among American adults was a potent 0.7 (roughly as high as the correlation between two different IQ tests) but by the late 1970s it had sunk to 0.57, where it remained through the 1990s and presumably today.

By 2006, roughly 26% of American adults, aged 25+ had a bachelor’s degree or more.  That means that the median university graduate, is in the top 13% of education.  If you’re in the top 13% of IQ, you’d have an IQ of 117 (U.S. norms), in other words, 17 points above the U.S. mean of 100.  But since the correlation between IQ and education is only 0.57, the expected IQ of university grads would be 0.57(17) + 100 = 109.69.

How close does this prediction come to the actual data?  According to a source provided to me by commenter C, the actual IQ of U.S. university grads (age 20-90) tested in the WAIS-IV 2006 norming  was 110.77.

Very close to the predicted value.

In 2006, roughly 17% of American adults, aged 25+ lacked a high school diploma or equivalent.  That means that the median high school dropout was in the bottom 8.5% of education.  If you’re in the bottom 8.5% of IQ, you’d have an IQ of 80 (U.S. norms), or 20 points below the U.S. mean of 100.  But since the correlation between IQ and education is only 0.57, we’d expect high school dropouts to have an average IQ of 0.57(-20) + 100 = 88.6.

The actual average IQ of Americans with only a 9th to 11th grade education (age 20-90) tested in the WAIS-IV 2006 norming was 88.77.

Again, very close to the predicted value.