This report explores the use of CCDF child care subsidy payment rates and practices to try to expand the supply of specific types of child care that are in shorter supply and focuses in particular on one of the most common policy levers—increasing the per child subsidy payment (also known as “differential” or “tiered” rates) paid to providers for children receiving these types of care. Although differential rates are used to support a variety of goals, this report specifically examines the following question: What is known about using subsidy rate policies and practices to expand the overall supply of priority child care options, either by incentivizing providers to start delivering the priority service or by incentivizing providers who already deliver these services to expand their efforts? (author abstract)