The Effects of Variable Omission in the Travel Cost Technique
重新审视旅行成本法中遗漏旅行时间和拥挤效应等变量导致的设定误差，从理论和实证角度分析误差大小与性质，对户外休闲需求估计和资源价值评估有参考意义。
The travel cost technique is probably the most widely used method for estimating outdoor recreation demand functions. Consequently, problems of specification have attracted much attention. Specification errors, due to the omission of travel time and congestion effects, have received the most recent attention-with the consensus being that the travel cost technique underestimates the true value of recreational resources if these variables are omitted (Gum and Martin 1975; Wetzel 1977; McConnell and Duff 1976). Yet, the effect of variable omission is likely to vary depending upon the type of activity, the existence of substitutes, and related factors. For this reason we reexamine, from both an empirical and theoretical perspective, the magnitude and nature of potential specification errors due to variable omission.