  In a recent article in PNAS, Case and Deaton show a figure illustrating "a
marked increase in the all-cause mortality of middle-aged white non-Hispanic
men and women in the United States between 1999 and 2013." The authors state
that their numbers "are not age-adjusted within the 10-y 45-54 age group." They
calculated the mortality rate each year by dividing the total number of deaths
for the age group by the population of the age group.
  We suspected an aggregation bias. After adjusting for changes in age
composition, we find there is no longer a steady increase in mortality rates
for this age group. Instead there is an increasing trend from 1999-2005 and a
constant trend thereafter. Moreover, stratifying age-adjusted mortality rates
by sex shows a marked increase only for women and not men, contrary to the
article's headline.
  We stress that this does not change a key finding of the Case and Deaton
paper: the comparison of non-Hispanic U.S. middle-aged whites to other
countries and other ethnic groups. These comparisons hold up after our age
adjustment. While we do not believe that age-adjustment invalidates comparisons
between countries, it does affect claims concerning the absolute increase in
mortality among U.S. middle-aged white non-Hispanics. Breaking down the trends
in this group by region of the country shows other interesting patterns: since
1999 there has been an increase in death rates among women in the south. In
contrast, death rates for both sexes have been declining in the northeast, the
region where mortality rates were lowest to begin with. These graphs
demonstrate the value of this sort of data exploration, and we are grateful to
Case and Deaton for focusing attention on these mortality trends.
