Mean population counts in Finland year, sex, and age group.
data.table with columns
sex gender coded as male, female (0, 1)
year calendar year 1981-2016
agegroup - coded 0 to 100; one-year age groups
meanpop the mean population count; that is, the mean of the
 annual population counts of two consecutive years; e.g. for 1990 
 meanpop is the mean of population counts for 1990 and 1991 
 (counted at 1990-01-01 and 1991-01-01, respectively)
Other popEpi data: ICSS,
  popmort, sibr,
  sire, stdpop101,
  stdpop18