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Markets rebounded sharply from a disastrous Christmas Eve.

The Dow rose 850 points Wednesday, the index’s biggest point increase since October 2008. It gained 3.9%, the biggest percentage gain since August 2015.

The S&P 500 soared 4%. The Nasdaq was up about 4.8%, pulling out bear market territory. Both indices had their best day since August 2011.

Wednesday was a rare respite from a very rough month for investors. Despite Wednesday’s gains, the stock market remains poised for its worst December since 1931.

“Investors went bargain shopping the day after Christmas, where stocks just got too cheap relative to earnings, future earnings, any reasonable assessment of earnings,” said Chris Rupkey, managing director of MUFG. “The coast is clear, back up the truck, investors are saying enough already, the world is not ending.”

Thin trading and a lack of big news often send stocks higher in the last week of December.

Stocks rose higher despite virtually no news — which may have been a catalyst in its own right. President Donald Trump has not tweeted Wednesday. Shortly after 2 pm ET, the White House announced Trump and the first lady traveled to Iraq on Wednesday. Recently, Trump has unsettled markets by signaling the potential firing of Federal Reserve Chairman Jerome Powell and a trade war escalation.

One piece of good news: Mastercard (MA) and Amazon (AMZN) both reported robust holiday season sales, suggesting rising wages and lower gas prices are helping boost consumer spending — the biggest contributor in America’s GDP.

But investors weighed that against a dour housing report from S&P/Case-Shiller, which showed the growth in home prices was at a two-year low. Shares of department store JCPenney (JCP) dipped below $1 for the first time and Ford (F) stock was down as much as 9% this week.

One good day isn’t a trend

The S&P 500 remains close to entering a bear market, ending the longest bull market in history. The Nasdaq is already in a bear market.

A partial government shutdown, Treasury Secretary Steven Mnuchin’s questions about banks’ health and signals that President Donald Trump could fire Federal Reserve Chairman Jerome Powell upset markets on Monday, sending the Dow down 653 points.

After markets tanked on Christmas Eve, Trump said Tuesday that he remains confident in Mnuchin, but he renewed his criticism of the Fed, accusing it of hiking rates too fast.

Those doubts come of top of worries about how sharply the US economy might lose steam next year.

“The markets are in panic mode that the US economy is tanking,” Stephen Innes, head of Asia-Pacific trading for online broker Oanda, said. “If the US economy turns south, global capital markets are in for a world of hurt.”

The only certain thing about the market this month is uncertainty. The slightest bit of bad news can turn a rally into a rout. For example, stocks were up nearly 400 points on Friday but ended the day down more than 400 points.

Asian markets rattled

In Asian markets, Japan’s Nikkei swung between gains and losses Wednesday before closing up nearly 1%. The shaky trading followed a 5% plunge on Christmas Day that dragged the Japanese index into a bear market. In China, the Shanghai Composite shed 0.3% on Wednesday.

Fears about slowing economic growth have been exacerbated by a series of unsettling moves from Washington in recent days.

The turmoil in Washington is making traders in other countries fret about the stewardship of the world’s biggest economy.

“Japanese investors are absolutely shocked by the lack of the leadership team in Washington,” Jesper Koll, head of Tokyo-based investment fund WisdomTree Japan, told CNN. “The reality is that the president no longer has a team of credible leaders to manage the American and the global economy.”

Global investors already had a laundry list of worries, including China’s slowing economy, the Trump administration’s trade war with China and the unpredictability surrounding Brexit.

“There’s a lot of uncertainty, and that’s one of the biggest things that the market doesn’t like,” Andrew Sullivan, a Hong Kong-based market economist, told CNN.

Some of the world’s biggest markets are yet to react to Wall Street’s Christmas Eve sell-off. Stock exchanges in London, Frankfurt, Hong Kong and Australia remain closed and will have to digest the recent turmoil when they reopen Thursday.