The linked article is problematic. There is a pretty agreed on correlation between IQ and income (the image obscures this). In the case of wealth the article claims that there is a non-linear relationship that makes really smart people have a low wealth level. But this is due to the author fitting a third degree polynomial to the data! I am pretty convinced it is a case of overfitting. See <a href="http://www.aleph.se/andart/archives/2007/04/cubic_terms_make_smart_people_bankrupt.html">my critique post for more details</a>.