My concern is that he didn't calculate internal rate of return (IRR) correctly, and adjust for market conditions when the female CEO was hired/fired. It's hard to tell without verifying the details.

For example, suppose a company hired a female CEO during the market bottom in 2002 and fired her before the crash in 2008. Then, that would cause the "female CEO" statistic to be inflated relative to the S&P 500. If you calculate the relative IRR, it's more correct.

I.e., instead of a buy-and-hold S&P 500 investment vs buying/selling when the female CEO is hired/fired, you should instead buy $100k of the S&P 500 and female CEO stock SIMULTANEOUSLY, and then cash out both holdings when the female CEO is fired.

If you buy-and-hold the S&P 500 for 12 years vs buy/sell during a female CEO tenure, that's an apples-to-oranges comparison. That isn't properly adjusting for the market conditions when the female CEO was hired/fired.

He didn't provide enough details for me to check. I'd need a list of female CEO Tickers, hire/fire dates, and split-and-dividend-adjusted share price on the two dates.