The Impact of Model Misspecification on Parameter Estimates in Mortality Models of the Gompertz Family

Trifon I. Missov, Max Planck Institute for Demographic Research
Laszlo Nemeth, Max Planck Institute for Demographic Research

We study a class of four mortality models with exponentially increasing hazards of death by senescent causes (the Gompertz family): the Gompertz, the Gompertz-Makeham, the gamma-Gompertz, and the gamma-Gompertz-Makeham. We quantify the bias in parameter estimators if we fit a model from this family that neglects non- zero extrinsic mortality or existing mortality deceleration. We present the resulting distortion in mortality measures imposed by the inaccurate parameter estimates.