User's Guide to Ratio Variables
作者讨论了社会科学中比率变量的使用争议。一些社会学家直觉认为，包含共同成分的比率变量之间必然存在虚假关系，而另一些则认为只有当比率本身而非其成分是理论关注点时，使用比率变量才合理。作者指出，这两种观点都基于对非实验研究中因果效应估计的错误理解。为了获得无偏估计，研究者通常需要控制一个主要的混杂变量Z（如人口规模），而将其他变量除以Z（即使用比率变量）就是一种控制方法。作者发现，与虚假性论点相反，这种控制方法不会引入偏差；但也不像另一种论点所认为的那样，仅限于比率本身具有理论兴趣的情况。因此，理论兴趣并非决定是否使用比率变量的可靠指南。
Some sociologists intuit a necessary relation between ratio variables with common components, and they warn that observed relations between such variables are likely to be artifactual. In rebuttal, other sociologists argue that the use of ratio variables is justified when the ratios themselves, rather than their components, are of Both arguments are based on mistaken ideas about estimating causal effects in nonexperimental research. To realize unbiased estimates, social scientists often must controlfor a dominant confounding variable Z (e.g., population size). One control procedure is to divide the other variables by Z, i.e., to use ratio variables. Contrary to the artifactuality argument, this control procedure does not introduce bias; but contrary to the argument, the control procedure need not be restricted to instances where the ratios themselves are of theoretical interest. Conventional wisdom notwithstanding, theoretical interest is not a reliable guide for determining whether or not to use ratio variables.