Lee Epstein
Lee Epsteing Ethan A.H. Shepley Distinguished University Professor
Lee Epstein
Published in 2004. Social Science Quarterly 85: 19-30.

Lee Epstein
Andrew D. Martin

In their article, Does Age Matter?, Carp, Manning, and Carroll group a continuous variable, age, into three categories or cohorts: 1= under the age of 46; 2=46-64; and 3=65 and older. When they enter this (now ordinal-level, treated as if it were interval-level) variable into a logistic regression model designed to explain judicial decisions in age discrimination cases (coded 0 if the judge ruled against the plaintiff alleging age discrimination and 1 if in favor of the plaintiff), it produces a positive and statistically significant coefficient; when they enter this same cohort-age variable into a model designed to explain outcomes in litigation alleging discrimination based on race or gender, it yields an insignificant coefficient. Taken together, these results lead the authors to conclude that age "matters" in precisely those cases in which they expect it to matter—age discrimination suits—and that it does not matter in those cases in which they expect it not to matter—race and gender discrimination suits.

As it turns out, though, this conclusion—and, more important, the inference that Carp and his colleagues reach based on their sample of data—rests entirely on their grouping decision. Specifically, if we respecify the models in precisely the same way as the authors but vary the cut-off points on the age-cohort variable, we find that for age discrimination cases, only 2 of 23 (plausible) cut-off points produce results in line with the authors’ expectation.

Click here for the article (.pdf).

The data we used in this article are available from Bob Carp at the University of Houston. Please email Lee Epstein if you are unable to obtain them.