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Rates of Mortality Improvement

Final Report Summary - ROMI (Rates of Mortality Improvement)

Project ROMI had three main goals: 1) Gaining a deeper understanding of population dynamics with declining mortality using mathematical demography 2) Visualizing mortality dynamics, especially with respect to period and cohort effects. 3) Developing a novel method to forecast mortality and, ultimately, life expectancy.
Ad 1) We have shown mathematically that populations with stationary fertility trajectories could become also stationary despite continually falling mortality. Depending on the fertility path, the transition phase to stationarity may exhibit damped periodic fluctuations similar to the classic stable population model.
Ad 2) Computer generated surface maps of death rates to visualize mortality dynamics have been in use since the 1980s. Instead of standard death rates, we plotted surface maps of rates of mortality improvement, i.e. the time-derivative of age-specific mortality. Among other things, those surface maps facilitate the detection of period and cohort effects. Two databases were created for this purpose. A software package called "ROMIplot" has been released to enable interested researchers to create their own surface maps of rate of mortality improvement.
Ad 3) We developed a novel model to project mortality. It has three characteristic features: a) It does not model death rates but their rates of improvement; b) it is probabilistic to take future uncertainty into account; c) it allows the incorporation of reference countries when the country of interest displays irregular patterns, which are implausible to continue into the future. In empirical comparisons, our model turned out to be at least as good as standard mortality forecasting models. In many situations it was even more accurate than other models.