Between 1961 and 1999, average life expectancy in the United States increased from 66.9 to 74.1 y for men and from 73.5 to 79.6 y for women. The spread of male life expectancy across US counties, as measured by SD, rose slowly in the 1960s, then declined steeply until 1983 (1.9 y), when it began to rise again to 2.3 in 1999; the rate of increase declined in the 1990s (). For women, cross-county life expectancy SD declined between 1961 and 1983 (from 2.0 y to 1.4 y), but rose steadily to 1.7 y in 1999. Cross-county life expectancy SD was always larger for men than for women.
SD of Life Expectancies of the 2,068 County Units in the United States by Sex
In the early 1980s, the absolute disparity between counties at the extremes of mortality advantage and disadvantage also began to increase. For example, the difference between life expectancies of the counties that make up the 2.5% of the US population with the lowest and highest mortality in each year rose from 9.0 y in 1983 to 11.0 y in 1999 for men, and from 6.7 y to 7.5 y for women (B). This widening gap was caused by stagnating improvements in life expectancy among the worst off, while the best off experienced consistent mortality decline (A). Between 1961 and 1999, male life expectancy in counties with the lowest mortality rose from 70.5 to 78.7 y; the corresponding rise for females was from 76.9 to 83.0 y. Trends in the worst-off counties were more punctuated: Life expectancy increased in the 1960s and 1970s for females and in the 1970s for males. Starting in the early 1980s, life expectancy of the worst-off females remained relatively stable (68.7 y in 1961, 74.5 in 1983, and only 75.5 in 1999); that of the worst-off men had a period of decline, rising again in the 1990s. The stagnation of mortality among the worst off was primarily caused by a slowdown or halt of the earlier decline of cardiovascular mortality, coupled with a moderate rise in a number of other chronic diseases, for both sexes as well as HIV/AIDS and homicide for men.
Annual Absolute Life Expectancy Disparity between the Counties with the Highest and Lowest Life Expectancies
groups counties by change in life expectancy, separately for 1961–1983 and 1983–1999, in relation to the sex-specific national average life expectancy change over the same period. shows the epidemiological characteristics of below- or above-average mortality reduction observed in . Dataset S2
and Movies S1
show the estimated life expectancy for individual counties and for all years between 1961 and 1999. Figures S1
show the absolute change in county life expectancy for 1961–1983 and 1983–1999. Between 1961 and 1983, counties whose life expectancy increase was (statistically) significantly larger than the national average were primarily in the rural Deep South and the Eastern Seaboard, in the West from the Mexican border into the Rocky Mountains for both sexes, in Alaska, California, and Hawaii for men, and in the Dakotas and along the Mississippi River for women. During this same period, life expectancy improvements were significantly below the national average in the Midwest and Southern California for both sexes, in the Mississippi Delta for men, and in parts of the West Coast for women. In this period, the best-performing counties had the lowest average starting life expectancy of all groups in (66.1 y for men and 72.0 for women; ), and the worst-performing ones had the highest starting life expectancy (68.9 for men and 77.6 y for women). This negative association between starting life expectancy and change in life expectancy supports the finding of shrinking cross-county mortality disparities. In 1961–1983, no counties had a statistically significant decline in sex-specific life expectancy at the 90% confidence level. The broad improvement of life expectancy observed during this period was primarily caused by major reductions in cardiovascular disease mortality for both sexes, compensating and surpassing the rise in cancers and chronic obstructive pulmonary disease (COPD). The distinction between those counties that performed better or worse than the national average in this period was primarily the rate of decline in cardiovascular diseases, with secondary effects from injuries and other noncommunicable diseases.
Change in County Life Expectancy in 1961–1983 and 1983–1999
Change in Probability of Dying in Specific Age Ranges between 1961 and 1983 and between 1983 and 1999, with Counties Grouped on the Basis of the Level of Change in Life Expectancy as in
Selected Socioeconomic and Demographic Characteristics of the Populations of the Counties Showing Significantly Above-Average, Average, and Below-Average (Including Stagnation or Decline) Life Expectancy Change
Between 1983 and 1999, male and female life expectancies had statistically significant decline in 11 and 180 counties, respectively (0.5% and 3.0% of the male and female populations); average decline in these counties was 1.3 y for both men and women. Another 48 and 783 counties had nonsignificant life expectancy decline for men and women (0.4% and 8.8% of the male and female populations), respectively. The average life expectancy decline in these counties was 0.5 y for women and 0.4 y for men, but these were not statistically significant because these counties were relatively small. Of the counties with statistically significant life expectancy decline, all for males and all but seven for females were in the Deep South, along the Mississippi River, and in Appalachia, extending into the southern portion of the Midwest and into Texas. There were also a number of counties with significant female life expectancy decline in the Rocky Mountain area and the Four Corners region, and one in Maine. Between 1983 and 1999, above-average mortality gain also became geographically more concentrated, and shifted to the Northeastern and Pacific Coast counties.
The decline in female life expectancy after 1983 was caused by a rise in mortality from lung cancer, COPD, diabetes, and a range of other noncommunicable diseases in the older ages (; detailed numerical results available in Dataset S1
). Female mortality from lung cancer, COPD, and even diabetes had also risen in 1961–1983, but this rise was surpassed by the decline in cardiovascular disease mortality. The rise in mortality for these causes in 1983–1999 was no longer compensated by the decline in cardiovascular mortality because cardiovascular decline became substantially smaller than it was in 1961–1983 (women in the worst-performing group, group 6, actually experienced a rise in cardiovascular mortality in the oldest age group). In 1983–1999, the rise in HIV/AIDS and homicide deaths in young and middle-aged men was a major contributor to male, but not female, life expectancy decline. Mortality from diabetes, cancers, and COPD in the older ages also worsened in men but these continued to be countered by relatively large reductions in male cardiovascular mortality.
Between 1961 and 1983, counties with life expectancy improvement above and below the national average had relatively similar income levels; average county income was lower in those counties whose life expectancy change was below average and indistinguishable from zero (group 5), but these represented <1% of the female population (). Black women formed a larger proportion of the population in counties with above-average life expectancy improvement than in those counties with below-average life expectancy change; the pattern was reversed for men. After 1983, gain in life expectancy was positively associated with county income. The proportion of blacks was higher in counties with life expectancy decline, especially for men, but there were no detectable patterns of sociodemographic factors across other county groups in .
If cross-county migration had been the only factor affecting any county's mortality, the SD of life expectancy in US counties would have declined from 1.89 y in 1993 to 1.71 in 1999 if emigrants had the same life expectancy as those who stayed in the county or origin; in practice it increased to 1.99 (). The SD in 1999 would have been 1.71 if emigrants had a life expectancy that was 1 y higher than those who stayed in the country of origin, and 1.78 if only those migrating to counties of higher life expectancy had a life expectancy 1 y higher than those who stayed in the country of origin or migrated to counties of lower life expectancy. In fact, only in extremely polarized migration scenarios—when migrants to counties with higher life expectancy have a 2.3-y advantage over those who stay in the county of origin—does the net effect of migration become an increase, rather than a decrease, in cross-county life expectancy SD (for comparison, the change in national life expectancy in the United States was 2.3 y between 1982 and 1999). In 1993, individuals migrating to counties with lower life expectancy came from counties with an average life expectancy of 76.9 y; those migrating to counties with higher life expectancy came from counties with an average life expectancy of 75.2 y (with similar ordering for 1994–1999). Therefore, at the county level, migration seems to have worked to dampen the rising cross-country mortality inequality.
Cross-County SD of Life Expectancy in a Migration Simulation