> The 0.4% is overwhelmingly concentrated in men who have sex with men. It's approximately an order of magnitude lower in women.

I added a note to interpret with caution because many factors can significantly affect this figure. Some states have an order of magnitude difference from others, potentially offsetting the MSM factor you mention [1].

> Based on your envelope math, I should have a >90% chance of having HIV

The envelope math was exposure not contraction. If you used or condom, or even just received oral, it's quite possible you didn't get HIV even if your partner did.

[1] Compare WY with GA - https://en.wikipedia.org/wiki/HIV/AIDS_in_the_United_States#...

> The 0.4% is overwhelmingly concentrated in men who have sex with men. It's approximately an order of magnitude lower in women.

True, but it's also true that male-to-female transmission is easier than female-to-male transmission, which makes the odds better for the man in any given encounter.

I'm not sure what the systemic effect is.

Depends on the country as well. They may be true in the US but it is not true in other counties.