ETA: The table linked by Landsburg has been called into serious question by Evan Soltas [H.T. CronoDAS]. I edited the post to leave only the table to provide context for the comment discussion of its status.
Economist Steve Landsburg has a post [H.T. David Henderson] about the supposed stagnation of median wages in the United States in recent decades. In the linked table median wages have risen for:
The error comes more from the map-warping power of political correctness than from the Simpson's paradox.
Edit: look at what happened to the then Harvard President Larry Summers when he discussed why women might be underrepresented in the sciences.
Simpson's paradox is a simple mathematical explanation for the error, "political correctness" is a complex socially-constructed one intimately tied up with particular political positions. Occam's Razor favors the former, overwhelmingly so.
There is no need to introduce the hypothesis that the error is due to people not agreeing with the particular political views of the Blue Party (which is what the "political correctness" hypothesis states), when simple math suffices to explain it.