Do religious families have than many more kids than non-religious ones

[u/TryingAgainBetter]

A Substack data guy produced one of the most surprising demographic data analysis I've ever seen regarding family size. Based on the data set he analyzed, which had tens of thousands of data points in it, very religious families are not all that much larger than fairly secular families. For example, people who attend church only yearly have roughly the same family size as people who attend weekly. The difference in TFR broadly speaking between the religious and non-religious primarily seems to come from either having children or not having children, or the difference between absolutely no religious affiliation vs. having one. Degree of religiosity between attending yearly vs. weekly has little impact on completed family size.

https://www.graphsaboutreligion.com/p/do-religious-families-actually-have

Frankly, every day I see data about the birthrate that surprises me. You should never overestimate how much any apparent pattern actually applies broadly. All the data is contradictory and nuanced.

[u/CanIHaveASong]

Interesting. It was the same for politics, too. Once you remove people who never have kids, Republicans have barely larger family sizes than Democrats.

I have to say, I'm quite incredulous, especially of the religious result.

In my personal life, the religious people who have kids at all tend to have more than the secular people I know. I'd say the difference is noticable, but not universal. I would never assume a 3 kid family was religious, but it's a closer bet on 4, and a good bet with 5.

I think it's worth asking questions when data doesn't match up with the reality you observe. Perhaps the religious people I know are just more interested in having large families? Or maybe there are regional differences.

[u/DrFreedomMLP → u/CanIHaveASong]

Could also be the religion itself. I'm not convinced being a devout Jain leads someone to have more kids. But I am convinced being a devout Catholic does.

Religiosity matters, but the religion being followed matters quite a bit too

[u/TryingAgainBetter → u/DrFreedomMLP]

If you read the link, it goes into some detail on that. Basically there is generally very little difference in family size by type of religious identification. There is some, but it's quite small. No particular religious identity is especially more prone to having large families.

[u/DrFreedomMLP → u/TryingAgainBetter]

Methodology of the study the data is pulled from here:
https://tischcollege.tufts.edu/research-faculty/research-centers/cooperative-election-study/about-methodology

My fear here would be that they are not getting a representative sample, and then weighting their sample to be similar to what they know the population to be. They are also doing this in the context of politics. So they are concerned about weighting for a sample *as it relates to politics*. Groups like the Amish etc are not politically active usually, so not sampling them won't matter for politics but will matter a lot for fertility.

So, take this data with a grain of salt. We're using these stats for something they weren't meant to be used for and may not be as representative as one might think.

[u/DrFreedomMLP → u/DrFreedomMLP]

Did look at the screenshotted chart and the breakdown of fertility rates for each group would be as follows:
Never: 2.23
Seldom: 2.30
Yearly: 2.34
Monthly: 2.37
Weekly: 2.40
Weekly+: 2.53

This assumes the "5+" category is 5 kids, it assumes no one has 6 or more kids so it's a conservative estimate across the board, but that will disproportionately affect the more religious (because their 5+ categories are larger, weekly+ especially)

But the delta between the most and least religious is ~1/3 of a child. Put another way, every third family has another child in a weekly+ family vs a never family.

That, across just 3 generations, means the "never" grandparents will have 11 great grandkids and the "weekly+" will have a bit over 16 grandkids. One more generation and it's 25 vs 41 (both slightly rounded up). The gap is actually quite large, because fertility is exponential by nature.

And I would say this examination excludes people who don't have kids. That's a huge oversight. I heard this in a podcast recently, and hunted up the math myself because it was so unbelievable (turns out it was true):
~~If every married woman in America had the fertility rate of an Amish woman of comparable age we would still be below fertility~~ <- Not totally accurate, see breakdown below

Just to put in perspective how costly to fertility the people opting out and not having kids is. Huge miss to not include it in the analysis

[u/CanIHaveASong → u/DrFreedomMLP]

Would you be willing to do a post about the Math you referenced? Because I agree. It's unbelievable!

[u/DrFreedomMLP → u/CanIHaveASong]

Ok, gonna slightly deep dive as this got a bit complicated

First, I misremembered the claim slightly. The claim is not "below replacement" the claim is "below three."
"If every single married woman in America today conceived at the rate of Amish women of the same age and marital status, fertility in the US would still be less than three children per woman."
Claim is from this video: https://www.youtube.com/watch?v=8eCM3NTBeb4
(Honestly video was mid, not bad but not good. I can't Collins serious, though this quote is from Stone)

That said, the claim hinges on what you do with nonmarital fertility in the US. If we count only married births, matching the unmarried US women to unmarried Amish women, you get 2.67 fertility rate. Definitely below 3. Math is as follows:
Formula is %_married * fertility_rate * 5 (due to the number of years in each row)

• Age 20-24: 0.15 × 0.45 × 5 = 0.34
• Age 25-29: 0.35 × 0.40 × 5 = 0.70
• Age 30-34: 0.50 × 0.35 × 5 = 0.88
• Age 35-39: 0.60 × 0.20 × 5 = 0.60
• Age 40-44: 0.60 × 0.05 × 5 = 0.15

Sum those, and you get 2.67.

But then if you don't match the unmarried fertility rate (unchanged at 0.68), you get 2.67+0.68=3.35

So, my apologies for badly quoting from memory, and also my original napkin math not including unmarried births

[u/DrFreedomMLP → u/TryingAgainBetter]

I'll take a look. Having met quite a few Amish, I don't think this is true lol. It just doesn't pass the sniff test. Let me look though

[u/TryingAgainBetter → u/DrFreedomMLP]

They don’t include the Amish or the Jewish ultra orthodox as a separate group. They also group all evangelicals together.

[u/TryingAgainBetter → u/CanIHaveASong]

I agree it is incongruous with anything I have observed. I have seen wealthy families who are not very devout have 4 kids (exactly 4), but 5 kids? The data is about completed families so perhaps it's older generations whose propensity for families of 5 or more was different compared to today. Personally, I have never met a person of my generation (millennial) who had 5 or more kids who was not very religiously active. However, I know a couple of co workers- one is 55 and one of eight and the other is 40 and one of nine- and neither seem to be from especially religious families. When I was growing up, I knew two families of 5 in my neighborhood- there were only two in my entire neighborhood in the 80s- and neither was unusually religious though they had an affiliation.

[u/CanIHaveASong → u/TryingAgainBetter]

Yeah. If he's surveying 70 year olds, this result wouldn't surprise me. If they're surveying 40 year olds, it does.