ABSTRACT
Adjusted rate differences can be produced by a generalized linear model with the rate as the outcome, the identity link, the Poisson family, and importance weights equal to person-time for each rate denominator. The power link can be used to fit rate difference models, rate ratio models, or something in between. If a power link intermediate between 0 and 1 is used, results can be converted to rate ratios or differences using marginal methods. The choice ratio (multiplicative) and difference (additive) models is discussed. Convergence problems may arise with rate difference models.
