Economics is the only field in which two people can share a Nobel prize for saying opposing things. Eugene Fama, Lars Peter Hansen and Robert Shiller all worked on financial markets efficiency and drew separate, if not opposing, conclusions. This is a welcome reminder that the dismal science has few absolute truths to offer.

Unlike Hansen, Fama and Shiller are mostly known for the conclusions they - or often, others - draw from their academic work. Fama is one of the founding fathers of the efficient market hypothesis (EMH), which roughly holds that financial markets always send the right price signals. Shiller, on the other hand, seems to have spent decades debunking the EMH, collecting empirical evidence that?markets are prone to bubbles and irrational exuberance.

An important practical insight of Fama's research is that it is difficult to beat the wider stock market over a sustained period of time. Empirical research supports this finding, and triggered the rise of passive investment funds that track stock market indices.

The authors are Olaf Storbeck and Viktoria Dendrinou, Reuters Breakingviews columnists.