By Elaine Buckberg, Steven Herscovici, Branko Jovanovic and James Reitzes ( July 17, 2017, 11:37 AM EDT) -- Several recent studies claim to show that competition is adversely affected when institutional investors hold significant shares in multiple firms within a "concentrated" industry, leading to higher prices and other effects.[1] Following on this research, Eric Posner, Fiona Scott Morton and E. Glen Weyl have proposed a remedy that would allow institutional investors to hold shares in only one company in a concentrated industry, or to limit their shareholdings to no more than a 1 percent total equity stake in the industry when holding shares in multiple companies. They also propose a "safe harbor" for stand-alone "purely passive" index funds that commit both to having no contact with management of companies whose shares they own, and to voting their proxies in proportion to other shareholders' votes....