Analysis-US tech stocks' market dominance reaches new heights and presents new risks

The charge higher in U.S. technology stocks has made broader indexes as reliant as ever on the group -- and more vulnerable should those market leaders trip up. With stunning gains over the past two months, the S&P 500 technology sector now accounts for more than 39% of the market capitalization of ‌the overall benchmark index, its highest on record and above the level it reached during the 2000 Internet bubble. "If the small number of tech stocks that have been leading this ‌market higher roll over, by definition, the indexes are going to roll over," said Matthew Maley, chief market strategist at Miller Tabak.