Tech stocks, central banks fuel 11% gain from summer low

Benchmark gauge back in black for first time since selloff

Central-bank stimulus and strong earnings from the largest technology companies combined to give U.S. stocks their fourth straight weekly gain and propel the Standard & Poor's 500 toward its best month since 2011.

The S&P 500 has jumped 11 percent from its summer low, with the surge in October led by commodities producers and technology shares, the very groups that fueled the August selloff. The gains put U.S. equities back in the black for the first time since the correction, and left the benchmark index just 2.6 percent from its all-time high.

"Stocks are back," said Robert Pavlik, who helps oversee $9.1 billion as chief market strategist at Boston Private Wealth. "We're back on track as far as a cheap money, quantitative easing, risk-on trade is concerned."