September 2003

New formula recalculates U.S. female life expectancy

A new formula may calculate life expectancy more accurately when the average age of death is in flux, according to a study published by John Bongaarts and Griffith Feeney of The Population Council, in the Proceedings of the National Academy of Sciences. The new formula shaves two years off the current longevity estimates for women in countries with rising life expectancies, such as the United States.

Currently, life expectancy is calculated using formulas originally developed in the mid-19th century. The authors argue that these formulas produce distorted estimates when the average age at death is changing due to unprecedented improvements in health care, medical technology, or other causes. In order to calculate more accurate life expectancy estimates, the authors constructed a new formula that integrates the rate of change in mortality. The new formula avoids an overestimation of life expectancy when the mean age of death is rising and an underestimation when the mean age of death is falling. The title of the study is "Estimating mean lifetime.”

Source: Proceedings of the National Academy of Sciences

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