Send us a textDo Companies Buy S&P500 Membership? A new working paper attempts to figure out why some companies make it into the blue-chip stock market index.In recent years there has been a huge shift away from active asset management and towards passive, index-tracking funds. The indices that these funds follow have in turn gained enormous power, becoming gatekeepers to the flow of trillions of dollars.Names like S&P Dow Jones, FTSE Russell and MSCI are the biggest index providers a...