Some of the nation's largest private-equity firms have formed the Healthcare Private Equity Association, a nonprofit trade association to be based in Chicago and intended to support educational and professional development of the healthcare private-equity community. "Healthcare is the largest sector of our economy . . . and it is also massive and complex," said Brian Miller, the association's founder and president, who is also a partner of Linden Capital Partners, a Chicago-based healthcare private-equity firm. "We need a central repository for research to be done and ideas to be exchanged."