Dow Jones industrial average ends day down more than 500 points, worst day of 2015

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NEW YORK —Global stock markets are getting a gut check this week.

The Dow closed down 531 points Friday, its fourth straight day of losses. It marked the worst week for the stock market since 2011, and is now at “correction” level,meaning a 10 percent drop off in a short period of time. It occurs when an adjustment needs to be made for an overvaluation of the stocks. It’s been 1,400 days since the last correction.

Around the world, major indexes also fell for the week and most are negative for the month.

Three big factors are driving this week’s worries:

1. Concerns are growing that China’s economy is slowing down faster than its government has said.

2. Investors had been preparing for the U.S. Federal Reserve to raise its benchmark interest rate in September. However, the central bank has been sending mixed signals. That’s dredging out the market’s worst enemy: uncertainty.

3. Oil prices dropped below the key $40 level to the lowest point since 2009.

The Dow dipped into correction territory, falling 10 percent from its most recent high hit on May 19.

The S&P 500 was also down 5.7 percent for the week, its worst weekly performance since 2011, while the Nasdaq fell 6.8% and was also close to correction territory.

The losses are just as bad, if not worse, abroad with some indexes in China and the U.K. stock market all now in correction.

How bad is China’s economic slowdown?

The latest red flag came Friday morning from China. The government reported that its manufacturing activity — a key sign of economic performance — hit a 6-year low in July.

After the government devalued its currency last week, Wall Street has become extra worried about the China slowdown.

Although Chinese officials say the economy grew 7 percent earlier this year, many experts wonder if it’s worse.

“There’s nobody that really believes that China is growing at 7 percent,” said Tim Anderson, managing director at MND Partners in New York. “They’re afraid to say to what degree their economy has really slowed down.”

Will the Fed raise rates in September

As if China wasn’t worrying investors enough, the odds of a Fed rate hike in September seems to have lowered.

Earlier this week, the central bank released the minutes from its July meeting, which showed some members are ready to go forward with a rate hike while others are concerned about the global economy and non-existent inflation in the U.S.

The uncertainty from the minutes — along with China — was a one-two punch that drove the markets down further.

“I am still saying yes [for September], but I have much less conviction,” says David Joy, chief economist at Ameriprise Financial in Boston. “It’s still an open question on whether they would move in September or not.”

Oil prices are at 6 1/2 year lows

And then there’s oil. Crude oil prices fell to again this week, and are flirting with the $40 a barrel level. A year ago a barrel of oil was about $100.

Oil is a lifeline of economic growth for many developing countries, which are also seeing their currencies lose value because of their economic exposure to China.

Brazil’s currency, the real, has fallen 9 percent against the dollar in just the past 4 weeks. Colombia, Chile, Vietnam and Indonesia have also seen significant currency drops against the dollar.

Less demand for oil hurts these country’s economies, which rely on China as a trade partner.

The fall in oil prices is hurting U.S. energy stocks too. Exxon and Chevron are down 25% and 38% respectively over the past year.