We used two approaches for estimating the “control” population, that is, the living population, and those who died from causes other than suicide and homicide. For our core analyses, we used the 1990 U.S. Census 1% micro-extract as the control population. Although this approach includes decedents from suicide and homicide as part of the control group, this represents only 0.25% of the population, so the error introduced by this approximation is negligible. The advantage of this approach is that the census extract is a precise 1% sample of the population born between 1949 and 1972 and alive at the beginning of our 1990–2004 observation window. The disadvantage of using single-year population data is that secular trends with respect to year-of-death (period effects) cannot be modeled because the controls yield no information about the population in the years beyond 1990. Hence, for regression analyses that included period as a covariate, we used an alternative approach to estimating the control population. In this second approach, we used estimates of the population for every year between 1990 and 2004 to produce a “time-averaged”
