Economist: Sustainable investing, once a niche area of interest, has moved into the mainstream. Earlier this month a survey showed that 75% of American asset managers say their firms offer sustainable-investing strategies, which focus on environmental, social and governance (ESG) issues. Almost 90% of fund managers think it is no longer just a fad. Young investors are driving the surge in interest: more than three-quarters of high-net-worth millennial and Generation Z investors have their assets reviewed for ESG impact.