Studies have shown there to be racial differences in vaginal tightness, and that these differences correspond to torso-ength and hip-width directly. In particular, white (non hispanic) women have the widest hips and the longest torsos and so in theory the loosest vaginas. Surprisingly, black women actually have the narrowest hips and thus the tightest vaginas, and shorter vaginal length than white women. Asian women sit in between with narrower hips than white women but wider hips than black women, and shorter vaginal length than black and white women. So this means that on average black women should have the tightest vaginas. While Asian women are the most likely to bottom out with an average size penis (which may or may not feel pleasurable), but may also feel overall looser and more gentle.

I haven't found any info on hispanics and native americans. But if I had to guess, based on South Europe, I'd guess white-hispanics sit somewhere in between white (non-hispanic) and blacks with narrower hips than whites, and shortee torsos than whites, but wider and longer than blacks. And for Native Americans I'd expect them to somehow be a cross between Asian and Black somehow, with narrow hips than all whites, but wider than blacks and shorter torsos than blacks and all whites, but longer than Asians.

So, my theory is guys are heavily visual because of this reason. Waist to hip signals the width of hips -- which tells us how good sex will feel like from afar. Torso height also tells us length, when combined with race. So yeah that's that.

Probably turns out that a ratio of 0.7 is a the ideal mix of tightness and length, compromised with an ability to give birth without complications. Less that 0.7, for example, might indicate unneeded looseness. Greater than 0.7 might indicate not enough length or poor physical health of the girl (unhealthy diet).

Generally, any deviations even at a healthy body weight may indicate hormonal imbalances or other things. Same way short height indicates likelihood of mental disabilities in men, like adhd and other things like that. So, IMO, hip to height to torso ratio is the female equivalent of height in men. It can't necessarily be changed as it deals with bones.

Although, a girl may he able to artificially widen her hips with hormonal supplements/prescribed pills there is a drawback for going too wide (less than 0.7 ratio).