It’s not easy being green, especially if you’re a fund manager. A decade or so ago, when mainstream politicians such as Britain’s David Cameron were petting huskies and embracing environmental issues, the stocks of renewable-energy producers were in vogue. But as in the dotcom boom a few years earlier, share prices ran way ahead of the potential for profits. An exchange-traded fund in global clean-energy stocks, set up by iShares in 2008, has lost investors 79% since its launch. Over the longer term, an analysis by Gbenga Ibikunle and Tom Steffen in the Journal of Business Ethics found that European green mutual funds had significantly underperformed their conventional rivals between 1991 and 2014.