Why do firms become widely held?

"We consider IPO firms from 1970 to 2001 and examine the evolution of their insider ownership overtime to understand better why and how U.S. firms that become widely held do so. In our sample, amajority of firms has insider ownership below 20% after ten years. We find that a firm's stock marketperformance and trading play an extremely important role in its insider ownership dynamics. Firmsthat experience large decreases in insider ownership and/or become widely held are firms with highvaluations, good recent stock market performance, and liquid markets for their stocks. In contrastand surprisingly, variables suggested by agency theory have limited success in explaining theevolution of insider ownership"--National Bureau of Economic Research web site.