Cost-shifting is either an economic situation where one group underpays for a service resulting another group overpaying for a service (shifting compared to expected burden) or where one group pays a smaller share of costs than before resulting in another group paying a larger share of costs than before (shifting compared to previous arrangement). Some commentators on health policy in the United States believe the former currently happens in Medicare and Medicaid as they underpay for services resulting in private insurers overpaying.