Five tech stocks drove 93% of S&P 500 rise since July

93% of the S&P 500's rise since late July came from five big tech stocks, MarketWatch reports. The S&P 500 tracks 500 large U.S. companies, so almost all the gain rests on a few giants while the other 495 added little. I'm wary for index-fund savers, because trouble in those few names drags the whole benchmark.