The major domestic equity indexes ended the trading day on Friday in negative territory, capping a day of heavy trading with investors mostly pulling back from initial concerns over an escalating trade dispute between the United States and China.

Trump unveiled an initial list of strategically important goods that would be subject to a 25 percent tariff effective July 6, a move China’s Commerce Ministry called “a threat to China’s economic interest and security.”

In response, China issued its own list of U.S. imports subject to tariffs, targeting soybeans, aircraft, autos and chemicals.

Since early May, the two countries have held several rounds of talks but have yet to reach a deal, as the United States pressures China to narrow a $375 billion trade deficit.

Friday also marked “quadruple witching day,” the quarterly simultaneous expiration of options and futures contracts, which tends to boost trading volume as investors replace expiring positions. As a result, volume hit the highest point since Feb. 8, when the S&P 500 sank to its lowest level of the year so far.

Companies considered the most sensitive to trade war worries were among the day’s biggest losers. Shares of Boeing, the single-largest U.S. exporter to China, fell 1.3 percent, while tariff-sensitive construction equipment maker Caterpillar and chemical company DowDupont were down 2.0 percent and 0.9 percent, respectively.

For the week, the Dow was down 0.9 percent while the S&P 500 rose 0.01 percent and the Nasdaq gained 1.3 percent, its fourth consecutive weekly advance.

Of the 11 major sectors of the S&P 500 six ended the day in negative territory.

The energy sector was the largest percentage loser, down 2.1 percent as oil prices fell more than 3 percent ahead of next week’s OPEC meeting.

Approximately 9.9 billion shares changed hands on the major domestic equity exchanges, as compared to the 6.9 billion share average over the past 20 trading days.

Industrial Production Falls

industrial production fell slightly in May amid a sharp drop in manufacturing output, the Federal Reserve said on Friday.

Overall industrial output fell 0.1 percent last month after an upwardly revised 0.9 percent increase in April.

The Fed measure of the industrial sector comprises manufacturing, mining, and electric and gas utilities.

May’s decline was driven by a 0.7 percent fall in manufacturing, the largest monthly decline since January 2014, with the largest drops including a 6.5 percent fall in motor vehicles and parts and 2 percent decreases in primary metals and apparel.

April’s reading was upwardly revised to show a 0.6 percent gain.

Mining production was up 1.8 percent and utilities output rose 1.1 percent.

Overall manufacturing output rose at an annual rate of 1.7 percent through May, while the index for mining surged 12.6 percent on a 12-month basis and utilities rose 4 percent in that period.

With output falling in May, the percentage of industrial capacity in use fell 0.2 percentage points to 77.9 percent.

Fed officials have traditionally looked to capacity use as among the signals of possible higher inflation.