The meaning of median compensation with a high school education

The problem with this statement

William Kristol's bad grade in economics - How the World Works - Salon.com

...For American men with only a high school education, Rodrik writes, median compensation has declined by 10 percent since 1980...

is that the average man with only a high school education in 1980 is probably not the same as the average man with only a high school education in 2008. In 2008 we're talking about someone who's either making some very bad decisions or who has a very significant cognitive disability. In 1980 the group would have included many people who would now go to college or trade school; back then these folks could enter the blue collar labor market and be reasonably well paid.

I think if one adjusted for IQ the income decline would be much less than 10%.

Odd to find myself almost defending Kristol here, as I do believe that much of America is being "Left Behind" - economically speaking. It's just that I have a hard time letting an illogical statement stand ...