Man, talk about vanity. I do the family genealogy. It's a lot of fun, even the various roadblocks some of my more idiotic ancestors toss in my way. Take this one, for example. One of the branches consisted of one large group of sisters living together in the 1930 Census, after both parents had died. They were all adults. Now, I had already gotten the 1900 and 1910 Censuses and used those dates for their birthdates. After finding the 1930 Census, I noticed there was something really off. Every single one of the females had knocked at least five years off their ages. One knocked off a whopping eight years of hers and her husband's ages. Argh! If I hadn't had the 1900 Census with all of them listed and using my keen powers of deduction (How could their parents plan to perfection what children they'd have and what genders in the next decade?) I'd have been just the teeniest bit confused. As it is, I'm just annoyed.
The only possible explanation other than vanity is if the census-taker asked a neighbor. I find myself hoping it was that, actually. Not that it matters.