Carol — Those graphs are indeed fascinating, and I discussed them a little bit here. I’d like to make a few more quick points in the context of the issues you raised.
Basically, there are a few strands of thought that get lumped together under “too many people are going to college.” The first idea is Murray’s: Too many jobs require bachelor’s degrees when they’re not really necessary. The graphs simply indicate that for a person of any IQ level, education increases income — which is not in tension with this thesis. A degree increases income because high-income employers require it, not necessarily because it’s actually improving people’s ability to do jobs.
Another strand of thought is that even in the current market, it’s better for a lot of people to go straight into the work force than to graduate from college. I think those graphs debunk this, but read the preceding sentence closely: I said “graduate from college.” A lot of people go to college, but fail to graduate, and they’re almost certainly worse off. The GNXP graphs don’t include “some college,” so it’s hard to tell for sure, though.