Welfare Effects, Omitted Variables, and the Extent of the Market
解释了Kling(1989)的发现：当价格完全相关时，单一价格变化的消费者剩余度量能无偏估计多重价格变化，并揭示了市场范围的定义与一般均衡需求函数在旅行成本模型中的应用。
This paper offers an economic interpretation of Kling's (1989) finding that single-price change measures of consumer surplus will provide an unbiased measure for a multiple-price change, provided the prices are perfectly correlated. The explanation lies in recognizing that correlation in this case serves to define the commodity extent-of-the-market. Using this link, the paper demonstrates how the insights involved in defining general equilibrium demand functions or equivalently residual demand models can be adapted to fit the issues raised with travel cost models in accounting for the effects of substitutes.