Exchange-traded funds investing in companies with responsible environmental, social and corporate governance practices lured a record USD 85 billion in the U.S. and Europe in 2020, and are still raking it in.

Pumped up by the flows, stocks in many of these funds are trading at frothy price-to-earnings multiples that are increasingly hard to justify. Take U.S. fuel-cell maker Plug Power Inc., for instance. The unprofitable company’s more than 2,000 percent rally since early 2020 outpaces even Tesla Inc’s.