Medica's private health exchange that offers four accountable care organizations (ACOs) in addition to an open network option has seen greater enrollment than anticipated, with over 50% of members choosing an ACO. The exchange uses a defined contribution model where employers pay 75% of costs and employees choose a plan. Employees seem satisfied with the ACO options that offer networks beyond narrow networks and provide savings of $300-500 annually compared to the open network. Member retention rates are high, at 95% staying with their initial ACO choice.