What's Happening to U.S. Mortality Rates?

A key factor affecting the cost of the Social Security program is how long beneficiaries live. Life expec­tancy is determined by mortality rates – that is, the probability of dying at each age. While mortality rates have been declining over time, progress has not been uniform. Sometimes mortality rates decline very rapidly, and sometimes they decline slowly. More­over, rates of improvement vary by age. For example, during most of the 20th century the mortality of in­fants and the working-age population fell faster than the mortality of retirees. This “age-gradient” matters for Social Security, since mortality improvements for young adults tend to help Social Security’s finances by expanding the size of the workforce paying into the system, while improvements at, say, age 65 tend to worsen it by increasing spending on benefits for longer-lived retirees. This brief explores the swings in the rate at which mortality has improved since 1900 and the impor­tance of the age gradient in these improvements over the period. It also takes a closer look at the years since 1969, when detailed data on cause of death are available. In retrospect, the factors leading to the speeding up and slowing down of mortality improve­ment are relatively clear. The future, as always, is harder to predict. This brief is the first of two on mortality rates; the second one will provide an inter­national perspective. The discussion proceeds as follows. The first section provides an overview of mortality trends and the age patterns since 1900. The second section focuses on the swings in mortality improvement in the last 40 years and the patterns by education level and by disease. The third section discusses the major drivers of these outcomes – such as developments in medicine, greater access to health care, the decline in smoking, and the rise in obesity. The fourth section explores the major factors that will influence the rate of improvement in mortality over the next 75 years. The final section concludes that the key debate for the long term is whether the future will mirror the past, with mortality rates of improvement fluctuating around 1 percent per year, or whether the big gains are behind us, with mortality improving less rapidly in the future.