4.4 - Comparisons over Time: County Life Expectancy Example

Example 4-3: County Life Expectancies, by Race, 1997-2001 Section

Murray CJL, Kulkarni SC, Michaud C, Tomijima N, Bulzacchelli MT, Iandiorio TJ, Ezzati M. Eight Americas: Investigating mortality disparities across race, counties, and race-counties. PLoS Med 3(90)e260. DOI: 10.1371/journal.pmed.0030260.

Figure 1 from this paper is reproduced below and provides another example of statistics calculated from surveillance data.. The outcome is life expectancy, (i.e. how long do we expect to live at birth) calculated for each county over a five-year period. The county rates are specific for 2 races (of 4: Asian, black, Native American, white) and gender. Color-coding the life-expectancies from the darkest purple (highest) to the deepest red (lowest) allows visualization of the differences in life expectancies. Notice lower life expectancies for both races and genders in the southeastern part of the country.

Why is there denser color in graphs for whites?

Whites are more evenly distributed throughout all counties, while there remained counties with too few blacks to calculate a life expectancy. (white areas on the upper graphs)

County Life Expectancies, by Race, 1997-2001


Would you agree that the northern Plains have the highest life expectancy, particularly for females?

Example 4-4: Life Expectancy at Birth in the Eight Americas (1982-2001) Section

The thesis of this Harvard paper is that health disparities in the U.S. can be described in terms of 8 population groups; in the authors’ terms, eight Americas. The researchers came to this conclusion searching for patterns as they grouped age- and gender-adjusted county life expectancies and other statistics by race and geographic area. Figure 3 in the paper is reproduced below.


The highest life expectancy represented by the black line is for whites living in the northern Plains states. The bottom blue line represents the life expectancy for blacks in urban areas. There is quite a difference. Note also the difference between men and women in life expectancy, regardless of population grouping. The Appalachian white population is contained in America 4 (purple line)