|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
June 2004 How Long Do We Live? Estimates of current life expectancy at birth are crucial to projecting public health care needs and pension expenditures. The United Nations Population Division publishes country-by-country estimates, ranging from a low of 37 years in Sierra Leone to a high of 80 years in Japan (1995–2000). In the United States, estimates are 74 years for men and 79 years for women as of 1997. These figures, though, may be a few years too high in countries with long life expectancies, say John Bongaarts and Griffith Feeney, two demographers who have analyzed past and future trends in mortality. Bongaarts, vice president and director of the Population Council’s Policy Research Division, and Feeney, an independent consultant, identify a distortion in the underlying calculations that generate life expectancy figures and provide a formula to amend it. Their paper, “Estimating mean lifetime,” was published in 2003 in the Proceedings of the National Academy of Sciences. The distortion, which Bongaarts and Feeney term the “tempo effect,” has long been recognized by demographers studying fertility; the authors are the first to apply the concept to mortality. In the case of fertility, tempo refers to the timing of childbirth. When women delay childbearing to later in life, the birth rate temporarily will appear to drop; conversely, when women have children at a younger age, the birth rate appears to rise, even if they eventually bear the same number of children as if they had started later. According to Bongaarts and Feeney, the tempo effect influences mortality rates in much the same way. Interventions to improve health, such as changes in diet or drugs to lower hypertension, raise the average age of death, whereas a widespread, deadly epidemic like AIDS can lower it. The effect is clearest in societies with high life expectancy. According to the demographers’ calculations, removal of the tempo effect reduces life expectancy for U.S. women by 1.6 years and for Japanese women by 3.3 years for the period between 1980 and 1995. A reduction of two or three years may not seem like a big difference on the individual level, but the societal implications are considerable. “In the long run,” Bongaarts says, “two or three years can have a substantial impact on the total future expenditures on pensions and health care for the elderly.” So how high can life expectancy rise? Scholars are divided into two camps: the optimists predict life expectancy as great as 100 years by 2050, and the pessimists think we may be nearing the maximum. Although the new findings do not resolve this debate, the study lends more support to the pessimists’ point of view—which may be good news in terms of future expenditures on programs for the elderly.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
