Can You Trust Census Data?
freakonomics.blogs.nytimes.com
freakonomics.blogs.nytimes.com
Also, the older generation is more likely to have the family structure where the man works and the wife stays at home. I would think there would be financial incentives for a wife to over report her age for senior benefits and her husband to under report so as not to be forced into retirement.
Census forms are not used to determine a individual benefits from govt programs or by companies to "retire" people.