Interestingly, there was a recent article in American Scientist recently discussing how the so-called "Flynn Effect" (described above as the gain of 3 IQ points per year) seems to be slowing and even ending in some places. Here is a link to the article:

http://www.americanscientist.org/template/AssetDetail/assetid/51985

The original research on Flynn Effect used mostly (but not entirely) scores from nonverbal tests (especially the Ravens). Data from many countries were examined.