Note, however, that there's newer evidence that says it's not just incompetent people that overestimate their own abilities, but "Kruger and Dunning’s main data is better explained by positing simply that we all have noisy estimates of our ability and of task difficulty."
<a href="http://www.overcomingbias.com/2008/11/all-are-unaware.html" rel="nofollow">http://www.overcomingbias.com/2008/11/all-are-unaware.html</a>