Throughout Wall Street’s December meltdown, analysts have been saying that markets were plunging despite plenty of evidence that the United States economy remains strong and corporate profit growth is healthy.

That argument finally found listeners on Wednesday, when early reports of a strong holiday-shopping season helped lift the S&P 500 by nearly 5 percent, its best day since 2009. The Nasdaq added 5.8 percent, and the Dow Jones industrial average rose just under 5 percent. That jump, over 1,086 points, represented the Dow’s best single-session gain ever, although a number of days have eclipsed that in percentage terms.

A substantial rise in crude oil prices added to the lighter mood, as did efforts from the White House to ease up on criticism of the Federal Reserve.

The rally continued in Asia, led by Japan, where stocks on Thursday opened 3.7 percent higher.

The rebound in the United States offered investors a much-needed reprieve from a decline that had picked up speed in December. Stocks had fallen for four consecutive days through Monday, and the drop had pushed the S&P 500 to within just a few points of a bear market — defined as a 20 percent retreat from its high.