Brandon even told me at signing (well, rather the guy beside me who had asked him that) he'd seen the graphs RJ made in the notes...

RJ obviously used this as a tool to loosely distribute larger groups of characters.

There probably is an higher percentage of rarer strengths on both sides among WO and WF, simply because the ability is more common among them (they've not culled out the female gene pool among sparkers the way AS have done, and both group marry and have children).

For the rest, all evidence points to strength coming exclusively from the soul (what happened to Lanfear, discrediting the hypothesis it was a body issue ought to put that debate to rest. There's no oddity with Rand, nor with any of the transmigrated Forsaken who all have their exact old strength), so the bell curve would be very close to the AOL's, but in practice I'm guessing it would be very different as the percentage of women whose ability is found is incredibly low (tens of thousand aren't found in the Westlands alone), and the ability is less present in various groups because of culling. I suck at statistics, but my feeling is that the sample among AS at least is probably so small in comparison to Westlands women with the ability, that how the women get found is so random (relying massively on women deciding to go being tested... and they have such a small window of opportunity to make that decision...) there would be tons of aberrations, for e.g. for a few hundreds years, on a sample of only 1000 women, very few subjects with the rare strengths might show up at all.