Since the 2008 financial crisis, investing has evolved more toward evidence-based strategies in which ideas are rigorously tested or backed by credible research. This according to an article by Bloomberg columnist Nir Kaissar.

“The problem,” Kaissar explains, “Is that evidence-based investing has been a bust over the last decade. Everything investors had been doing wrong, according to the evidence, turned out to be right. While I think the last 10 years are going to turn out to be an anomaly, I wouldn’t be surprised if evidence-based portfolios become a tougher sell for the average investor.”

Kaissar notes that while the data available a decade ago suggested that investors should invest globally and across more styles, “their timing couldn’t have been worse. U.S. growth stocks have been among the best performers over the last decade.”

Kaissar concludes, “The conundrum is that the results of a few years shouldn’t override decades of evidence, and nothing precludes U.S. growth stocks from enjoying a star turn occasionally. But if they continue to dominate markets, it won’t be easy for investors to persuade themselves to hang on to their new evidence-based portfolios.”