Baykan for consumer price index (CPI): a measure of the (weighted) average price of a particular set of consumer goods. The CPI informs consumers as to how consumer goods prices are changing over time. consumer’s surplus: the difference between the most a consumer is willing to pay and the actual price paid for a good, typically calculated for the market as a whole (i.e., for all units sold within the market, rather than for just one consumer). consumption expenditure: the sum of all expenditures on consumer goods by households in a given period. contestable market: a market with no barriers to entry or exit, allowing any potential firm to very easily begin or cease operations within that market. Baykan 2016.