Index Investing Wins on Math. It Loses on Boredom.

The empirical case for index investing over active stock-picking has been available for decades, and most people who've seen the data agree with it in principle. The gap between agreeing with the data and actually behaving accordingly is where most investment outcomes are decided, and it has almost nothing to do with math.

Active management fails most people not because the strategy is impossible, but because it requires constant decisions, and constant decisions create constant opportunities to panic-sell during a downturn or chase a rally that's already over. Index investing's real advantage isn't a better return distribution — it's removing most of the decisions that behavioral finance shows people get wrong.

Understood this way, the "boring" criticism of index investing is actually the point. A strategy that requires almost no ongoing decisions is a strategy that can't be sabotaged by the investor's own psychology, which turns out to be the biggest risk in most portfolios anyway.