An expert-based framework for probabilistic national population projections: the example of Austria.

This study recommends a probabilistic scenario approach for population projections. The benefits are better information, ease of adoption, and expert opinion on the mean and range of uncertainty. The study answers whether it matters if high and low variants cover 85% or 95% of the range. An assumption of piece-wise linear random paths may underestimate the variance of the resulting population age distribution. A more realistic random path would have short-term fluctuations with some degree of autocorrelation. The expert-based probabilistic approach is applied to Austria. Official projections to 2050, account for 3 alternative migration assumptions and the usual fertility and life expectancy assumptions. Austria may have an absolute deficit of 60,000 persons after 2025. Population aging will increase from 19.7% to over 30%. The mean age of population will reach 50 years. The social implications of the alternative degrees of population aging are likely to have significant effects, such as on the pension system. The results of a test of the sensitivity of results for 85% and 95% confidence intervals and the impact on population size and old-age dependency outcomes reveal larger standard deviations and differences between fractiles with the 85% assumption of all cases lying between high and low values. Differences were larger between 85% and 90%, although not very significantly, than between 90% and 95%. When assuming short-term fluctuations, there was a greater range of uncertainty in the first 20 years than a standard linear interpolation, but long-term projections had lower standard deviations.