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>I did take calculus in high school, but I barely remember it

Probability calculus, not calculus in the sense of integration and differentiation.

>So I don't understand your notation

P(x) is the background probability of x. P(x|y) is the probability of x given y.

>I'm not sure if this would compound over generations

It's already had plenty of time to compound over generations, to whatever extent it does.

>the chance for birth defects goes from around 1% to 3-4%, about the same as a woman in her late 30s/early 40s having a child.

Indeed, which shows how silly your theory is. I mean, are you really suggesting that a slightly higher incidence of e.g. cystic fibrosis in Pakistani communities somehow makes it more difficult for them to integrate? That's such utter nonsense that you shouldn't be surprised if people infer some kind of malicious intent behind your comment.

[supreme_sublime]

>It's already had plenty of time to compound over generations, to whatever extent it does.

I'm not sure what you mean, most westerners don't make a habit of marrying their cousins.

Because of this compounding it means that the risks would be much higher than 3-4%, which is what we see in the data.

>I mean, are you really suggesting that a slightly higher incidence of e.g. cystic fibrosis in Pakistani communities somehow makes it more difficult for them to integrate?

It seems as though birth defects aren't the only way that inbreeding negatively affects offspring. It also appears to lower intelligence[0], while also increasing mental health issues.

[0] - https://link.springer.com/article/10.1007%2FBF01068128

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>Because of this compounding it means that the risks would be much higher than 3-4%, which is what we see in the data.

This is pure speculation on your part, as far as I can see. Do you have any data to back this up? It's also not the case that all Pakistanis routinely marry their cousins generation after generation. (The prevalence of cousin marriage is very variable within different Pakistani communities.)

>It seems as though birth defects aren't the only way that inbreeding negatively affects offspring. It also appears to lower intelligence[0], while also increasing mental health issues

You're cherry picking an old paper with a bad methodology. The result could easily be explained by the IQ of the parents being correlated with their likelihood of entering into a cousin marriage. As IQ is largely inherited, this would then lead to a difference in IQ between the two groups of children, even when controlling for SE status.