There's an old (bad) joke bout statistics (especially averages): They're like bikinis - what they reveal is interesting, but what they conceal is essential.
Statistics reveal that Engineering majors earn more (on average) than Economics majors, who earn more than Business, and Philosophy majors, respectively. But what these statistics conceal is that the choice of major is not random - not everyone has a knack or interest for engineering. In fact the sorting is pretty one-dimensional. As my undergraduate Money and Banking prof used to say, "theres people who can do calculus and people who can't."
That's not the news. What is, as Free Exchange points out, new research shows that individual differences in ability within each major explains most if not all of the difference. After all, an exceptional student in philosophy can go on to a great career as a lawyer.
Here's the bad news for the artsy-fartsies: the research underlying on which the post is based long-run lifetime earnings. So, if you're a philosophy major, be patient. You'll be surpassing your business major classmates around the time your kids are following in your footsteps as philosohpy majors.