Here are some stats from Wikipedia regarding availability of manpower
Military age 17-45 years old
Available for military service 67,742,879 males, age 18-49 (2005 est.),
67,070,144 females, age 18-49 (2005 est.)
Fit for military service 54,609,050 males, age 18-49 (2005 est.),
54,696,706 females, age 18-49 (2005 est.)
Reaching military age annually 2,143,873 males (2005 est.),
2,036,201 females (2005 est.)
Active personnel 1,426,713
Reserve personnel 1,458,500
For discussion’s sake, let’s acknowledge that the bulk of the 3 million in service is lower ranking...which they are. We will call that 60%. That = 1,800,000.
Let’s also identify them as the younger cohort that enters the military, that is, from about 18-23 years of age. That represents 6 year groups. Divided equally that would be 300,000 per year entering service in the eligible younger cohort. More than 2/3 of that is male, but we’ll allow that 200,000 males are in the new cohort in all services each year. (The 2007 Army active duty recruiting goal was 80,000, so that tracks.)
Your numbers tell us that 2.1 million come of military age each year. Compared with the year group cohort of 200,000, that means that 10% enters the military.
For the Romney family that would mean that 1 of the 6 should have served, because the military is much smaller now that it was as early as 10 years ago when it was 750,000 troops instead of 450,000 that we have now. Obviously, in the Viet era is was considerably larger.
Of my 4 children, 4 have served.
In short, many American families are not pulling their fair share. Blue-blood and upper class families are even worse.