"momentum is clearly based on behavioral explanations, including herding, anchoring, confirmation bias and the disposition effect. Because momentum has performed well historically, it’s clear that these behavioral biases have likely existed for a long time. And human behaviors tend to persist even after the biases are discovered and made well known. After all, that’s what makes us human."

http://www.etf.com/sections/index-investor-corner/swedroe-why-momentum-struggling?nopaging=1