Demand
Demand for child care is expressed by parents through willingness/ability to pay a certain price for a given unit of care.
Subsidies (e.g., vouchers, state contracts with providers) allow working parents who need but cannot afford to pay for services to exercise demand for the care they need. (However, below market rate subsidies allow low-income parents to exert influence only in those sectors of the child care market that accept below market payments for care.)