Response to Baker and Fugh-Berman's critique of my paper, Why has longevity increased more in some states than in others?

Dean Baker and Adriane Fugh-Berman have published a critique of a study I performed in 2007, entitled Why has longevity increased more in some states than in others?" One of the conclusions I drew from that study was that medical innovation accounts for a substantial portion of recent increases in U.S. life expectancy. Baker and Fugh-Berman claim that my study was subject to a number of major methodological flaws. Many of their claims pertain to the role of infant mortality; the definition of drug vintage; the issue of age adjustment; and the appropriateness of controlling for AIDS, obesity, and smoking in the analysis of longevity. In this article, I make the case that their claims about my study are largely incorrect. I show that infant mortality was not an important determinant of the growth in U.S. life expectancy during the period that I studied, and that my estimates are completely insensitive to the inclusion or exclusion of infant mortality. Controlling for the age distribution of the population also has essentially no effect on the longevity equation estimates. I argue that my definition of drug vintage, based on the initial FDA approval year of a drug's active ingredient, is quite reasonable, and it is consistent with the FDA's evaluation of the therapeutic potential of new drugs. I argue that controlling for AIDS, obesity, and smoking in longevity analysis is entirely appropriate and consistent with the epidemiological literature. Baker and Fugh-Berman express deep skepticism about my study's conclusion that medical innovation has played a very important role in recent U.S. longevity growth, but they offer no explanation of why life expectancy increased by almost a year during 2000-2006, a period of increasing poverty and obesity and declining health insurance coverage.