Population figures from the Census Bureau (2010). Veterans from the Veteran's Administration (September 2016). There is a modest error introduced by the lack of time matching of the population cohorts to the veteran cohorts, although it does not have much effect on the percentages.
The populations shown are for men and women combined. The rate for men is roughly 1.7 time the total in younger cohorts. The rate for women is roughly 0.3 times the total in younger cohorts. In older cohorts, the proportion of veterans who are men is higher and the male share of the total population is lower.
The rate of military service for men under age 45 is less than 10%, while a majority of men age 70 and older served in the military.