College graduates not as intelligent?

Inductivist looked into the General Social Survey and found that the mean IQs of white college graduates has been dropping:1960s 113.721970s 110.591980s 108.041990s 104.422000s 105.12Remember that the popualtion mean is around 100, with a standard deviation of 15. That means that since the 1960s the college graduate has gone from being, on average, in the 17.5th percentile to the 37th percentile of the population! What's going on here? I think it has to be the fact to a great extent a college degree is now substitute for a high school diploma, the pool is getting larger and so of course less select. I noticed in high school that looking at SAT scores from the 1980s that Mississipi had a higher average than Massachusetts! That totally shocked me, until I noticed that the proportion of high school graduates taking the SAT was on the order of 10% in Mississipi while in Massachusetts it was closer to 60%. One of my teachers assumed that this was the reason for the slow but steady decrease in average SAT score since 1960 before recentering in 1995. She explained that when she was in high school the SAT was something that only the elite students would be assumed to take. Today of course it is something that only the dumb avoid.