Stocks shook off morning losses on Monday and surged in the afternoon to send the Standard & Poor’s 500 index to its best day in a week. It’s the latest turn for a market suddenly prone to quick shifts not only day to day but also hour to hour, as investors question whether President Donald Trump will really risk a trade war.

The S&P 500 lost as much as 0.6 percent shortly after trading began, only to finish the day 1.1 percent higher after rising 29.69 points to 2,720.94. It’s reminiscent of what happened Friday, when stocks reversed course on speculation that Trump was only making an opening bid when he promised to impose stiff tariffs on imported steel and aluminum, rather than a final offer.

The Dow Jones industrial average jumped 336.70, or 1.4 percent, to 24,874.76, and the Nasdaq composite gained 72.84, or 1 percent, to 7,330.70. Both came back from early morning losses.

“It’s incredibly difficult to try to understand the whims of this current administration and to try to make forecasts,” said Emily Roland, head of capital markets research for John Hancock Investments. If a trade war does occur, it would hurt the global economy and the profit growth that companies have been producing, two of the big drivers for the market.

Watchdog highlights U.S. oil output

A global energy watchdog says booming production in the United States will meet most of the world’s growth in demand for oil in the next few years.

The International Energy Agency believes U.S. oilfields will offset slow growth from OPEC.

The group, based in Paris, issued its annual oil market report on Monday. The resurgence in U.S. production is the most prominent change since the group’s last forecast.

The agency continues to worry that globally, investment in new production has not recovered from the oil price plunge from mid-2014 to 2016. If not enough is spent on exploration, that could lead to future shortages and price spikes.

Walmart to offer prepared meals

Walmart will start offering prepared meals at its stores for the first time, a move that could help the nation’s biggest grocer sell more food while siphoning customers from restaurant chains.

Ten different meals are now available in 250 stores, and the program will expand to 2,000 locations by year’s end, Walmart executives said in an interview.

The company also is introducing four $15 meal-kit options in stores, expanding a business that had previously only been offered online through outside vendors.

Prices of the prepared meals will range from $8 to $10, and varieties include pot roast with mashed potatoes and chicken enchiladas.