The Bias Due to Omitting Quality When Estimating Automobile Demand
这篇短文指出，在估计汽车等异质商品的需求弹性时，如果忽略质量变量，会导致价格弹性被低估；基于Levinsohn（1988）的模型，加入质量变量可使估计的价格弹性提高80%以上。
The conclusions of policy-oriented market studies often hinge upon the size of an estimated demand elasticity. Few of the researchers who have estimated such elasticities have utilized a variable designed to measure the subjective concept of quality. If quality both significantly affects the demand for a heterogeneous good and is positively correlated with price, omitting quality from a demand regression will lead to a downward bias in the estimated price elasticity. Using Levinsohn's (1988) model of the automobile market as a framework, this note shows that including quality variables can increase the model's estimated price elasticity by more than 80 percent. Copyright 1991 by MIT Press.