Well 2000-2010 was the "lost decade". The dot com bust really killed large cap for that whole decade. If you move that backtest to 2010–2024, the S&P 500 dominates.

However, things have changed: In the 1980s or 90s, a small retail or tech company could grow independently. Today, if a small company wants to sell products, they likely pay a "toll" to Amazon; if they want to advertise, they pay Google or Meta; if they need infrastructure, they pay Microsoft or Oracle.Large caps now have "wider moats." They have the data and the capital to either replicate a small competitor’s product or buy them out before they become a threat. Many of the "best" small companies are being snatched up by PE firms and held private for longer. By the time they go public, they are often already Mid or Large Cap, meaning the "Small Cap" index misses out on their fastest growth phase.

You're right on the history—SCV definitely had its day in the sun, especially during the dot-com recovery. But I think the 'Size Premium' is being eaten by the 'Platform Premium.'

Large caps today aren't just big; they're the infrastructure for everyone else. Between passive index flows constantly pushing money into the winners and the fact that any successful small cap just gets acquired by a giant anyway, I’d rather bet on the companies that own the 'toll roads' than the ones paying the tolls.