The idea of investing with a social purpose is gaining ground. The broad category of sustainable and responsible investing grew 38 percent in the United States from 2016 to the start of 2018, to $12 trillion in assets under management, according to the US SIF Foundation. That represented one out of every four dollars of the $46.6 trillion under management, the group noted. A wide range of investments were held, including mutual funds, annuities, E.T.F.s and closed-end funds. Morningstar reported that 2018 marked the third consecutive year of record flows into sustainable funds; the number of sustainable funds also jumped nearly 50 percent. So far, most sustainable investments are held by institutional and high-net-worth investors. Negligible amounts are held in workplace retirement plans.