File:Impact-of-costs-active.jpg

Investing is a sum-zero game: the dollar-weighted performance of all investors is equal to the performance of the market (hypothetical bell curve on the right). After costs, the curve is shifted to the left: few high-cost active investors beat the index every year. Low-cost index funds and ETFs have returns close to that of the index, outperforming most active investors. Figure inspired by several Vanguard publications (no specific source).