I oversee the team that puts together the Fortune 40 Under 40 list, our once-a-year ranking of the most influential people in business under age 40 (head here to check out this year's list). And for as long as we've been doing it, the topic of the number of women on the list -- specifically, the lack thereof -- has been an issue.

I'm happy to report that it's become less of an issue. This year we have impressive women like Marissa Mayer, the 39-year-old CEO of Yahoo YHOO -3.08% who became the youngest person to head a Fortune 500 company the year she stepped in; Olivia Garfield, CEO of UK water company Severn Trent and one of five women CEOs -- of any age -- on the FTSE 100; VijayaGadde, general counsel of Twitter TWTR -3.79% and the only woman on the executive team; and Elizabeth Holmes, whose blood-diagnostic startup Theranos is valued at $9 billion. (Read our June cover story on Holmes, "This CEO is out for blood.")

But there are only 15 women on the list. 15 out of 40 is not parity -- far from it. And that's where the complaints come in.

Of course we agree: we need more women on this list. And we'd love to have half of the 40 be women. But the deficit on our list reflects the deficit in reality. It also reflects a truism about women in business I've come to realize. When it comes to women under 40, the universe of candidates whose business achievements (typically that's revenue, funding, size or scale of company) match men of the same age group is much smaller than we'd like it to be. But when you look at women between 40 and 44, the universe of powerful women explodes in number -- and their roles are much bigger. The sweet spot for women in business, I would argue, is ages 40 to 44.

I can't even count the number of times we've come across a new name during the 40 Under 40 research process who we think is a shoe-in for the list only to discover she's just missed the cutoff and is actually 40 or 41. This year, to cite just one example, we were thrilled to learn about a young divisional CEO at a major bank. We were briefly elated in the office -- discovering new people in very big jobs is the holy grail for this list -- until we learned she'd turned 40 just months prior. This kind of disappointment has happened to me so many times over the years that I have a word for it: forty freude; it's schaden freude, of the 40 under 40 variety. We're so happy for their success; we only wish they were still eligible.