Robert J. Barro attempted to elaborate on David Ricardo's proposal that these entities and loans are interchangeable because 
Robert J. Barro attempted to elaborate on David Ricardo's proposal that these entities and loans are interchangeable because consumers internalize budget constraints. That idea is the Barro-Ricardo equivalence theorem. An alternative to one of these entities designed to correct a negative externality created by Arthur Pigou is a cap-and-trade system. When introduced into an equilibrated market, they can cause deadweight loss by driving a "wedge" between consumers and producers. For 10 points, name these entities that come in Pigovian, estate, value added, sales, and income varieties, a percentage of a transaction that goes to the government.
Robert J. Barro attempted to elaborate on David Ricardo's proposal that these entities and loans are interchangeable because consumers internalize budget constraints.
taxes [Accept any kinds of taxes, like Pigovian taxes, income taxes, or sales taxes.]