I am pleased to be able to join in the discussion of the article by Luo (in this issue) on age, period, and cohort (APC) modeling in demographic research. Demographers have had a long fascination with various forms of accounting frameworks, and thus APC modeling was a natural topic for the demographic literature.
My interest in these models arose sometime in the mid-1970s, when I was part of a team teaching a short course on categorical data analysis. One of the “students” was especially persistent, both wanting to know precisely how to implement the computer programs but also the many details not in the lectures or the notes I distributed. His questions were always penetrating, and my answers tended to stretch out into the breaks and dinners. We spent a couple of evenings talking about research problems. That was my introduction to William (Bill) Mason.
One of Bill’s late-night questions...
