One interesting aspect of this post is how some of the explanations rely on people believing other explanations.
This is most obvious for #5 (signaling). The signaling explanation relies on prospective employers believing that economic majors are better suited for the relevant jobs. This could be because the employers believe in one of explanations (1)-(4) (the effect would be strongest if employers believed in explanations (1) or (3) themselves). Or it could be that they have just observed empirically that economics majors tend to do better, so they are causally agnostic but still prefer economic majors. I talk about this sort of thing more in my post http://lesswrong.com/lw/inm/signaling_of_what_precisely/
You also note in #4 (pre-existing desire to make money) that students with such a desire may be more inclined to choose economics because they believe that employers value the signal (#5).
One interesting aspect of this post is how some of the explanations rely on people believing other explanations.
This is most obvious for #5 (signaling). The signaling explanation relies on prospective employers believing that economic majors are better suited for the relevant jobs. This could be because the employers believe in one of explanations (1)-(4) (the effect would be strongest if employers believed in explanations (1) or (3) themselves). Or it could be that they have just observed empirically that economics majors tend to do better, so they are causally agnostic but still prefer economic majors. I talk about this sort of thing more in my post http://lesswrong.com/lw/inm/signaling_of_what_precisely/
You also note in #4 (pre-existing desire to make money) that students with such a desire may be more inclined to choose economics because they believe that employers value the signal (#5).