NEW YORK, Jan 15 : After years of watching technology stocks drive the U.S. bull market, investors are betting the rally will broaden to industrial, healthcare and small-cap companies, with a chance they can catch up and assert market leadership. Stocks such as Nvidia, Alphabet and Broadcom have buoyed the market's enduring rally, in which the S&P 500 has risen over 90 per cent since the bull market began more than three years ago. But investors have become wary of expensive tech valuations