Saturday, January 01, 2005

More on Life Expectancy Projections

In a recent post, I noted that leading demographers think the Social Security Trustees' assumptions about longevity understate the decline in mortality and thus program costs. This is relevant to the ongoing debate about the magnitude of the program's shortfall. It has become common for those who are against reforming the system now to point out that the economic growth rate assumed by the Trustees is low relative to the last 10 years and that higher growth will boost system finances. One should also look at the other assumptions to see if they are too optimistic or pessimistic. I did this in this earlier post. Brad DeLong provides some commentary here and gives his perspective about what aspects of long-term fiscal policy are in crisis.

In yesterday's New York Times, Robert Pear writes a pretty good article about this topic, "Social Security Underestimates Future Life Spans, Critics Say." The issue is well captured in these paragraphs:

For the American population as a whole in the last century, most of the gains in life expectancy at birth occurred from 1900 to 1950. But most of the gains in life expectancy among people who had already reached age 65 were seen after 1950.

Last year an expert panel advising the Social Security Administration found "an unprecedented reduction in certain forms of old-age mortality, especially cardiovascular disease, beginning in the late 1960's."

The panel said Social Security was wrong to assume a slower decline in mortality rates among the elderly in the next 75 years. Rather, it said, the government should assume that mortality will continue to decline as it did from 1950 to 2000.

Ronald D. Lee, a professor of demography and economics at the University of California, Berkeley, said: "I foresee death rates of the elderly in the United States continuing to decline at the same pace they have declined since 1950. In fact, there is evidence that the pace of decline in other developed countries has accelerated in recent decades."
The article then tries to include opposing points of view:

Further, some population experts foresee developments that could wind up buttressing the forecasts of the Social Security Administration. S. Jay Olshansky, a professor of epidemiology and biostatistics at the University of Illinois at Chicago, said the era of large increases in life expectancy might be nearing an end, with the spread of obesity and the possible re-emergence of deadly infectious diseases.

"There are no lifestyle changes, surgical procedures, vitamins, antioxidants, hormones or techniques of genetic engineering available today with the capacity to repeat the gains in life expectancy that were achieved in the 20th century" with antibiotics, vaccinations and improvements in sanitation, Dr. Olshansky said.

Indeed, he said, without new measures on obesity and communicable diseases, "human life expectancy could decline in the 21st century."
Two things are missing from this discussion.

First, for Social Security's financing, it matters whether the improvements in life expectancy occur early or late in life. Reducing infant mortality is a net plus for Social Security financing, because it will increase (in a couple of decades) the ratio of workers to beneficiaries. Reducing old-age mortality is a net negative for Social Security financing, for the opposite reason. Some of the issues being discussed here pertain to mortality early rather than late in a person's life.

Second, this discussion of obesity misses the important point that while higher obesity rates will lower Social Security retirement expenditures, they may increase Social Security disability expenditures and reduce tax revenues. It is not clear that the combination is a net plus for financing. It also misses the impact on Medicare, which is even more likely to be negative, since obesity is an important predictor of many chronic conditions (like musculoskeletal injuries, heart disease and diabetes).

But I thought the article was generally pretty good and worth a read.

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