"A blindfolded monkey throwing darts at a newspaper's financial pages could select a portfolio that would do just as well as one carefully selected by experts," Burton Malkiel famously argued in his classic 1973 book, A Random Walk Down Wall Street. Malkiel may have given too little credit to monkeys. Start with the record: U.S. large-company mutual funds have routinely failed to beat the Standard & Poor's 500 index since S&P began keeping score in 2002. Over the past five years, for example, 73% of active funds have fallen short of that benchmark. Today's fund families may appear well-stocked with...