U.S. stocks closed lower Friday, pressured again by falling oil prices, which drove the indexes to weekly loses of more than 3.5%—the second straight week of declines.

The New York Stock Exchange closed at 1 p.m. Eastern Time, while other financial markets also saw earlier closures on Black Friday.

The Dow Jones Industrial Average DJIA, +0.19% fell 178.74 points, or 0.7%, to 24,285.95, the S&P 500 index SPX, +0.29% off 17.37 points, or 0.7%, at 2,632.56, while the Nasdaq Composite Index COMP, +0.36% retreated 33.27 points to 6,938.98, a decline of 0.5%.

Read:Why share buybacks aren’t the stock market’s safety net

For the week, the Nasdaq tumbled 4.3%, the Dow ended the week 4.4% lower, while the S&P 500 notched a week-on-week decline of 3.8%.

According to Dow Jones Market Data, this week’s performances for all three major indexes marks their worst Thanksgiving weeks since 2011.

What’s drove the market?

Crude oil’s bear market worsened Friday, as investors wrestled with growing output from the U.S., President Donald Trump’s entreaties to key producers to keep prices lower, and generally rising inventories, despite a recent cold snap in many oil-consuming regions. The slide in oil prices weighed heavily on energy stocks, as 9 of the 10 of the biggest losers in the S&P 500 Friday were from shares of companies with links to the energy complex.

Read:A death cross is forming in U.S. oil, underlining the unraveling of crude prices

Investors also keyed in on developments in European politics, after the U.K. and European Union both announced progress on Thursday in outlining their future relationship after Britain exits the EU.

In Asia, markets faced serious pressure that rippled onto U.S. shores, after The Wall Street Journal reported that the U.S. government attempted to persuade foreign allies to avoid telecommunications equipment from China’s Huawei Technologies Co.

The reports highlight nagging tensions between Beijing and Washington centered on tariffs and the Trump administration’s claims of apparent abuses of intellectual property rights and espionage by Chinese tech firms.

President Xi Jinping and Trump are scheduled to meet in Buenos Aires on the sidelines of the G-20 summit next week.

On the bright side, the holiday shopping season appears to be off to a good start, after a report from Adobe Analytics showed that Thanksgiving online shopping rose 28.6% from last year, data that boosted some retailers during trade Friday.

What are strategists saying?

While falling oil prices are causing investors to worry about the slowing global economy, it is the rise in the U.S. dollar—resulting from an overseas slowdown—that will have the most direct impact on S&P 500 earnings, Jeff Kravetz, regional investment director at U.S. Bank told MarketWatch.

“Dollar strength could be a serious headwind for earnings going forward,” he said, because much of S&P 500 companies’ sales growth is derived abroad.

“It’s another down day, which is concerning,” Karyn Cavanaugh, senior market strategist at Voya, told MarketWatch. “The market continues to be worried about slowing global growth,” she said, adding that today’s drop in oil prices reinforces this fear.

“Investors are worried because the last time we saw oil really plummet, back in 2015, we also saw a serious slowdown in global growth,” Cavanaugh said.

“But there’s a real disconnect between market sentiment and the actually economy.’ she argued, which puts markets in a position to have a significant ‘Santa Clause’ rally, as she expects holiday sales figures to continue to show that “consumers are healthy and they’re out there spending money.”

Which stocks were in focus?

Shares of retailers Macy’s Inc. M, -1.30% , Target Corp. TGT, +0.65% and Best Buy Co Inc. BBY, -1.61% are in focus as Black Friday sales kickoff. Macy’s stock fell 1.8%, while Target shares were down 2.8%, and Best Buy stock was up roughly 0.7%.

Retail trade was one of the Dow’s bright spots Friday, after data from Adobe Analytics showed strong growth in online shopping Thanksgiving Day. Walmart Inc. WMT, +0.52% shares rose 1% Friday, while Walgreens Boots Alliance Inc. WBA, -0.08% stock advanced 1.3%.

Shares of energy-related firms were under pressure Friday, as the price of oil was down 6% on the day and more than 21% in November, so far. Marathon Oil Corp. MRO, +2.37% shares fell 4.6%, TechnipFMC Plc FTI, -0.47% stock retreated 4.2%, Devon Energy Corp. DVN, +3.22% stock fell 5.7%, and shares of Concho Resources Inc. CXO, +0.55% shed 6.3%.

Rockwell Collins US:COL shares rallied 9.2% Friday, after Reuters reported that Chinese market regulator has given conditional approval to United Technologies Corp.’s US:UTX takeover bid.

Which data were in focus?

The Markit flash reading on manufacturing PMI fell to 55.4 in November, a three-month low.

How did other markets trade?

Chinese stocks fell Friday, with the Shanghai Composite SHCOMP, +0.03% down 2.5%, while the smaller Shenzhen Composite 399106, -0.03% tumbled 3.6%. Japanese markets were closed for a public holiday.

In Europe, stocks ended the trading day mixed, with the Stoxx Europe 600 SXXP, -1.02% edging up 0.4%, and the FTSE 100 UKX, -1.29% down 0.1%.