The sample is very small, and mostly from the same areas, and again the stats are skewed by the fact the recruiting was done on a purely voluntary basis, nowhere thorough, and there's no way to know what percentage of all potential channelers from those areas they represent, but it won't be all that high (those women were from northern Murandy/southern Andor, women who had time to reach the rebel camp in the month between Egwene opening the Book to every woman and the departure for TV. It's a sample of a few hundred women that doesn't include the women recruited in the Salidar days. AS do not awake the ability of learners too weak to become AS - they simply turn them away, it's only weak wilders they agree to take in to teach them enough so they'd survive. The weak ones found in the Salidar days would have been turned away, but for a month in Northern Murandy, Egwene ordered that no one be turned away anymore. The rest of those women come from countryside around Dragonmount during the months of siege, an area where women would be far more likely to have tried going to TV to be tested in their youth, and in which the percentage of unfound ability must be abnormally smaller than in most other areas (probably not all). Among those recruits would also be an abnormal percentageof women who had gone to TV before but had been turned down as too old or too weak, but now Egwene's edict let all these women from around TV the possibility to join after all, no matter their strength or age).

In the TR the stats were skewed completely the other way, with the ability being above the normal percentage (closer to percentage of previous millenia), and with a lot of the women tested of significant, above median strength.

There would be a minimum of 2000 female channellers to recruit in the population of Caemlyn alone (if you calculate it at 1% of occurence of the ability in the global population, it's not generous, nor is it generous to put the female pop of Caemlyn at 200,000 as Lower Caemlyn has grown massively since RJ said in a Q&A the pop of Caemlyn was around 500,000 people).

And keep in mind all the evidence point to strength being determined by the soul. If there are genetic factors involved, they are genetic factors that attract naturally souls with a strong strength (and no, it's nothing to do with physical strength or big bodies... from the evidence we have, there seems to be a corollation with "soul" personality (those traits in which Rand and LTT are very close and which seems inherited from the soul and not genetic or from life experience, the whole nature vs. nurture aspect). From Siuan to Nynaeve to the Forsaken, the only woman (or man) of substantial strength we know who doesn't have a strong willed, stubborn personality is Moghedien, and for all her personality flaws, she's still strong willed and stubborn in her way - she couldn't be so good in TAR without that. We know strong personalities can have a weak ability (Morgase, Sorilea are examples), but we haven't got strong channelers with a weak personality, and it's even more flagrant in sparkers. And it's got nothing to do with confidence given by channelling, as we know from examples like Sharina and even more Nynaeve.