A new brief describes attribution, a key component of payment reform. Attribution done wrong in a shared savings payment model can create incentive to cherry pick out less lucrative or difficult patients and disrupt existing provider-patient relationships. Attribution is the process of defining the population that a provider network is responsible for managing under a shared savings contract. Effective attribution helps both consumers and providers. Consumers know who is responsible for their care and who to call with a problem. Providers know who they are responsible for, giving them every incentive to invest in care management and other appropriate services to keep people well. Provider networks share in the savings that consumers and providers generate together through better health. The brief outlines how prospective attribution models that connect providers and patients at the beginning of the payment timeline protect consumers from cherry picking and payers from the associated costs.