The article is misleading. At first blush he appears to be arguing that the Vanguard Total Stock Market Index Fund does not live up to its claim of accurately representing the entire US stock market because it underweights small cap stocks. But that's not really what he's arguing--instead, he is arguing that you will get the best returns by overweighting small cap stocks in your portfolio. So he's saying that Vanguard should in fact inaccurately represent the total US stock market, by overweighting small cap stocks. That makes no sense. If you want to tilt towards small caps, you should buy a total market fund and add a small cap fund, or buy a fund that holds itself out as a total market fund with a small cap tilt. But a fund that calls itself the "Total [US] Stock Market" should represent just that. Otherwise, if that's what I want, I have to buy that fund, then add some large cap exposure to "untilt" the tilt.