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Statistics seminar: "Probabilistic Population Projections for All Countries"

Seminario di Statistica

28/10/2013 dalle 11:00 alle 13:00

Dove Dipartimento di Scienze Statistiche - Via Belle Arti 41 - Aula III

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Adrian Raftery, University of Washington and University College Dublin

Abstract: Projections of countries' future populations, broken down by age and sex, are widely used for planning and research. They are mostly done deterministically, but there is a widespread need for probabilistic projections. I will describe a Bayesian method for probabilistic population projections for all countries. The total fertility rate, female and male life expectancies at birth are projected probabilistically using Bayesian hierarchical models estimated via Markov chain Monte Carlo using UN population data for all countries. These are then converted to age-specific rates and combined with a standard demographic projection model. This yields probabilistic projections of any population quantity of interest. These new statistical methods have been used by the United Nations to produce their most recent population projections for all countries. The results suggest that world population will increase more than had recently been believed likely, reaching between 9 and 13 billion by the end of the century, with no end to population growth this century. The population of Africa, in particular, is likely to grow, from about 1 billion now to between 3 and 5 billion. The results also indicate that the Potential Support Ratio (roughly the number of working age people per retired person) will almost certainly decline dramatically in most countries over the coming decades. The results also suggest that the current UN high and low variants underestimate uncertainty for high fertility countries, and overstate uncertainty for low fertility countries, mostly in Europe.