American Fertility Still Runs in Families: A Short Update
Excluding fantastic answers substantially strengthens my original results
While re-reading my “American Fertility Still Runs in Families” I noticed some sloppy work on my part. In the General Social Survey, the maximum reported number of siblings is 68! Perhaps someone is counting a massive number of polygamous half-siblings, but it’s far more likely that this respondent is lying or misunderstood the question. The same goes to a lesser degree for all of the sky-high sibling responses.
(Note: The GSS caps responses to “number of children” at 9, so this variable doesn’t have the same credibility problem).
Question: What happens to the results if you exclude fantastic responses?
Answer: The estimated tendency of fertility to run in families markedly increases.
See for yourself. Here are the original results for 1972-2022, counting all respondents:
Here are the revised results after excluding the roughly 3% of respondents who claim to have more than 10 siblings.
The magnitude of the key coefficient rises by 13%!
My original results are broken down for the 20th versus 21st centuries. These, too, get stronger once you discard respondents with more than 10 siblings.
20th Century - Original Results
20th Century - Updated Results
The key coefficient is 11% higher.
21th Century - Original Results
21th Century - Updated Results
Fully 17% higher after throwing out the hard-to-believe respondents.
Would I have posted these revised results if they undermined my original thesis? Yes, conscience requires it. Once I realized my initial oversight, the only scenario where I wouldn’t have written a full new post is the one where the results barely changed. In that case, I would have simply posted an update at the end of the original essay.
It's plausible TBH. I think GSS max is wrongly to low, I've known plenty of families with between ten and fourteen kids all the same mom. Not just my grandmother's generation either, but current families with the mothers in their thirties.
I think for extremely high number though, and I didn't look into the data, it depends on framing. Does it say full blooded? I've known guys personally with around fifty children between multiple wives (not polygamy, just four or five marriages over eighty years), girlfriends, mistresses, and one night stands which makes having eighty siblings plausible if you count halves. I mean Al Pacino (age 84) has a two year old for example. My own kids have at least four halves that I know about (but they don't), wouldn't be surprised if a couple others knocked my door one day.
I find fertility numbers tend to skew like many things, i.e. lots of big families, lots of zero families, and a whole lot of nothing in the middle (5 to 9).
My dad has 10 siblings and my grandmother has 12!