It's hard to imagine more beloved U.S. stock trades at the start of 2016 than going long bank and technology companies. Or, for now, a more painful one.

Shares of financial and information-technology companies in the Standard & Poor's 500 Index tumbled as much as 3.1 percent, their biggest losses in four months and the most in the index today, as another China-induced rout spread through U.S. equities. Confidence cratered and investors turned skittish about the most economically sensitive long bets amid renewed concerns of slower global growth.

The fifth-straight month of slowing in Chinese manufacturing triggered a selloff that halted Shanghai trading before the U.S. market opened. While the Nasdaq Composite Index fell as much as 3.2 percent, the most since August's correction, some of 2015's favorites were much harder hit.

The so-called "FANG" stocks — Facebook Inc., Amazon.com Inc., Netflix Inc. and Google's parent Alphabet Inc. — slumped 4 percent, with all four members falling to the lowest in at least two weeks. Meanwhile, all but two companies in the 87- member S&P 500 Financials Index tumbled, led by declines of at least 3.4 percent for JPMorgan Chase & Co. and McGraw Hill Financial Inc.

"Today is a knee-jerk reaction to the weaker data out of China. The sector reaction seems to be one of nervousness," said Alan Gayle, senior strategist for Atlanta-based Ridgeworth Investments, which has about $42.5 billion in assets. "If you believe that the U.S. economy is going to turn south, then the selloff in tech and financials makes perfect sense. We do not share that view."

Financial stocks have gained favor in the wake of last month's interest-rate hike, the first in nearly a decade. Investors chasing earnings growth have been enchanted with tech stocks, helping to push the group to a 15-year high a month ago. The two groups had rallied at least 76 percent in the past four years.

These two industries are favorites among strategists, including Goldman Sachs Group Inc.'s David Kostin, who recommends an overweight allocation to each. BMO Capital Markets Corp.'s Brian Belski and Scotia Capital Inc.'s Vincent Delisle also have overweight recommendations for both.

Today's rout started the year off with a thud after a lackluster 2015 for many investors. Michael Antonelli, an institutional equity sales trader and managing director at Robert W. Baird & Co. in Milwaukee, asked whether the bull- market rally could be "sputtering out."

"The general tone to start the year is one of very tepid expectations for 2016," he said. "That's remarkable because typically you see a bullish tone to start a year. At least you have recently."

For Gayle, a disappointing U.S. government jobs report for last month, due on Friday, would do more to color his outlook than one day of weakness. He maintained an overweight recommendation on the technology and financial industries, betting that the economic expansion will continue through this year and further buoy these stocks.

"We're going to take a day like today in stride."

Subscribe Now

Access to authoritative analysis and perspective and our data-driven report series.

14-Day Free Trial

No credit card required. Complete access to articles, breaking news and industry data.