Fear is back in the market.
Investors are worried about slower economic growth in China, a gloomier outlook for U.S. corporate profits and an end to easy money policies in the United States and Europe. They're also fretting over country-specific troubles around the world -- from economic mismanagement in Argentina to political instability in Turkey.
Those fears converged to start a two-day rout in global markets this week, capped by a 318-point drop in the Dow Jones industrial average Friday. It was the blue-chip index's worst day since last June. The Dow plunged almost 500 points over the two-day stretch.
The Standard & Poor's 500 index fell 38 points, or 2.1 percent, to 1,790 Friday. The Nasdaq composite fell 90 points, or 2.2 percent, to 4,128.
Among Western Pennsylvania stocks, First Niagara Financial Group was the hardest hit, falling $1.26, or 12 percent, to $9.08. The Buffalo-based bank issued a 2014 forecast below the expectations of some analysts.
Other big losers on a percentage basis were 3-D printer ExOne Company, falling $3.98 to $50.59; AK Steel, off 44 cents to $6.25; and Alcoa, which shed 63 cents to finish at $11.44.
Only four stocks in the 58-stock Post-Gazette/Bloomberg index of regional stocks advanced, but even they were up less than 1 percent.
Despite the sell-off, U.S. stocks remain near all-time highs after surging 30 percent last year. The S&P 500 is 3 percent below its record high of 1,848 on Jan. 15
U.S. stocks have not endured a correction -- a drop of 10 percent or more over time -- since October 2011.
In Asia on Friday, Japan's Nikkei 225 slipped 1.9 percent to close at 15,391.56; Hong Kong's Hang Seng shed 1.2 percent to 22,450.06; and Seoul's Kospi dropped 0.4 percent to 1,940.56.
The trouble began Thursday after a January survey showed a drop in Chinese manufacturing activity. Days earlier, China reported that its economic growth last year matched 2012 for the slowest pace since 1999.
"It is interesting how even a mild tremor in China's growth causes such anxiety around the world," said Eswar Prasad, professor of trade policy at Cornell University.
Slower growth in China is bad news for countries that supply oil, iron ore and other raw materials to the world's second-biggest economy.
Since the global financial crisis hit in 2008, the Federal Reserve has flooded markets with cash to push interest rates lower and encourage U.S. businesses and consumers to borrow and spend. But last month, as signs of growing economic strength emerged in the U.S., the Fed cut back -- reducing its monthly bond purchases to $75 billion from $85 billion. It also said that it expected to reduce the bond-buying further "in measured steps" at upcoming meetings.
The Fed meets again Tuesday and Wednesday. Many economists expect the central bank to cut the purchases again -- perhaps to $65 billion a month.
Len Boselovic and the Associated Press contributed to this story.