The Persistent Near-Linear Increase of Life Expectancy at Birth in Industrialized Countries: Explanation and Prospects for the Future

John R. Wilmoth, University of California, Berkeley

Recent studies have demonstrated a persistent near-linear increase in life expectancy at birth in industrialized nations over the past 50 years. Such a pattern stands in sharp contrast to the predictions of most mortality forecasts, which typically anticipate a slowdown in this trend. Such expectations derive from a key assumption of standard forecasting methodology, namely, a constant age pattern of mortality decline. Drawing on past evidence about an “aging of the mortality decline,” we build four hypothetical scenarios of future mortality trends. Two scenarios hold the age pattern of mortality decline constant over time, while the other two assume a gradual shift in this pattern toward older ages. These calculations illustrate that the aging of the mortality decline could be a key mechanism driving the near-linear increase of life expectancy at birth. In light of these results, we suggest that a revision of standard mortality forecasting methodology should be considered.