Swap out your S&P 500 fund for a random large cap fund (say VLCAX) and, whoops, worse CAGR and worse Sharpe ratio over the same period for your strategy. You c

Swap out your S&P 500 fund for a random large cap fund (say VLCAX) and, whoops, worse CAGR and worse Sharpe ratio over the same period for your strategy. You can prove you would've made money by backtesting anything.