That's true and a very good point worth remembering. But we're also talking about two things that are literally mostly the same. In the S&P 500, 100% of your money is in the S&P, in the total stock market fund, 80% of your money is in the S&P. Yes that other 20% matters, and that's why the returns are never the same. And it's even possible that one day their returns would be wildly different, but generally they have been very similar