CFO vs. CEO Insider Buying

I'm kind of skeptical of 'insider buying' signals, because I remember executives being totally clueless about our stock return, basically believing that after a big fall the price would rise and vice versa. Share issuance, meanwhile, has a pretty strong literature and I have found it valuable (yet another factor my old boss argued was not usable by me going forward because it would be covered under his interpretation of our confidentiality agreement). It seems this plays out in looking at CFO vs. CEO purchase, from a new paper by Wang, Shin and Frances:

We find that CFOs earn statistically and economically higher abnormal returns following their purchases of company shares than CEOs. During 1992-2002, CFOs earned an average 12-month excess return that is 5% higher than that by CEOs.