Evidence of learning in the stock market

This is a bit of an old article, but the idea of stock market learning came up in class on Wednesday and ethics all of last week, so I will mention market learning in the context of governance.

Short version: it used to be that you could get a higher return by buying firms with good governance (Gompers, Ishii, and Metrick, 2003)  (as measured by the Gompers-Ishii index) and shorting poorly