In economics, the excess burden of taxation, also known as the distortionary cost or deadweight loss of taxation, is one of the economic losses that society suffers as the result of taxes or subsidies.  Economic theory posits that distortions change the amount and type of economic behavior from that which would occur in a free market without the tax. Excess burdens can be measured using the average cost of funds or the marginal cost of funds (MCF). Excess burdens were first discussed by Adam Smith.