No valid statistic says how many women had it all, and the figure circulating online has no research behind it. The evidence shows that trade-offs were nearly universal and satisfaction is high anyway. The series' verdict is that where institutions refuse to underwrite a promise, luck fills the gap: the promise wasn't wrong, it was unfunded.
No research supports any 'percent who had it all' figure. Hewlett's childlessness numbers describe elite women only, and high late-life satisfaction scores are limited by survivorship and adapted expectations.