Ex ante returns are not the same as ex post returns. Borrowing cheap money to buy an S&P500 ETF would have paid off handsomely since 2008, because the market's

Ex ante returns are not the same as ex post returns. Borrowing cheap money to buy an S&P500 ETF would have paid off handsomely since 2008, because the market's gone up. If the market had crashed, you'd be in trouble. Similarly, given the fact that the market as a whole has gone up in period X, it should be no surprise that companies buying their own stock on margin have outperformed the market.