On the Knowledge@Wharton, Mark V. Pauly, of PSC & PARC, and Genevieve Kanter of the Perelman School of Medicine discuss the impact of changes to the Stark Law, which prevents doctors from self-referral, and the effectiveness of accountable care organizations (ACO).“I would be even more enthusiastic about ACOs if it had been shown that they actually improve the coordination of care,” says Kanter.