The Washington Post's Heather Long explains why the latest drop in the stock market shouldn't worry investors. (Heather Long,Lee Powell/The Washington Post)

U.S. stock markets seesawed again Friday, capping a head-spinning week that wiped out as much as $3 trillion in U.S. stock market value as investors fled from equity funds.

The Dow Jones industrial average saw a more-than 1,000-point swing, or about 4.2 percent, on Friday, in one of the market’s worst weeks since the 2009 financial crisis. The broader Standard & Poor’s 500-stock index gave up early gains and slid into negative territory — before clawing its way back into the black.

The Dow finished up 330 points, or 1.39 percent, at 24,191. The S&P 500 gained 38.5 points, or 1.5 percent. And the tech-heavy Nasdaq ended ahead, too, gaining 97.3 points, or 1.44 percent.

Investors remained torn. The massive Trump tax cut should provide a huge stimulus to an economy already rushing ahead at full employment, boosting profits and growth. At the same time, fears are growing that interest rates will jump as the federal government borrows massive amounts to cover its growing deficits.

“There’s a lot boiling over in this pot,” said Edward Yardeni, president of Yardeni Research. “The stock market clearly has concerns with what’s happening in the bond market, and the bond market is becoming increasingly concerned with both monetary and fiscal policies.”

Investors, who in January set a monthly record for sinking money into equity funds, pulled their money out at a record pace in the week ending Feb. 7, according to EPFR, a Cambridge, Mass., data firm that has tracked such information since 2000. Investment in inflation-protected bonds rose.

Some analysts believed the stock market swoon did not reflect deeper economic woes.

“This is a technical-driven sell-off, rather than one reflecting a significant deterioration in fundamentals,” Mohamed A. El-Erian, the chief economic adviser at Germany-based financial giant Allianz, said in an email. He added such sell-offs “are particularly unsettling to investors because it is hard for them to point to a familiar culprit relating to economics, geopolitics or the corporate world.”

But El-Erian said that these corrections “tend not to contaminate the broader economy as long as fundamentals are strong, which is the case today. The global economy is growing in a synchronized fashion, corporate balance sheets are strong, and banks are well-capitalized.”

Investors are worried about fiscal and monetary policy. The Treasury Department last week quietly announced that the federal government is on track to borrow nearly $1 trillion this fiscal year — President Trump’s first full year in charge of the budget. That is almost double what the government borrowed in fiscal 2017.

At the same time, the Federal Reserve has said it expects to raise rates three times in quarter-point increments, a modest start to returning to historically normal rates after the long recovery from the Great Recession of 2009. Moreover, the Federal Reserve has indicated that it will slowly reduce the amount of Treasury bonds it holds, potentially raising interest rates further.

The concerns reverberated around the world. Global markets, especially in Asia, fell sharply Friday after U.S. stocks went into correction territory, dropping 1,000 points for the second time in a week. 

In Europe, however, the reaction was more measured, with the main stock indexes posting losses just above 1 percent.

The mercurial week had some analysts rethinking their positions. On Tuesday, Chris Rupkey, managing director and chief financial economist of MUFG Union Bank, issued a note to investors saying, “The stock market is better than you think. Bet on it.” And, “Don’t be fooled by the modest decline in openings today.”

On Thursday, a more gloomy Rupkey told investors that “the era of low interest rates is at an end which means the proverbial punch in the punch bowl is leaving the party. And fast! The stock market is a leading economic indicator and right now it points the way for the economy straight down.”

Big retail investment houses continued to urge calm. Fidelity noted that since 1920, the S&P 500 has experienced an average of three 5 percent corrections a year, a 10 percent correction once a year, and a 20 percent correction every three years.

But there were also concerns of an economic shift more profound than a correction of valuations.

Moody’s ratings service issued a note Friday predicting that “the federal government’s balance sheet is set to deteriorate materially.”

Moody’s said that “over the long run, the direct fiscal impact of the tax reform will also be amplified by a larger interest bill, both due to faster accumulation of debt and an accelerated increase in market interest rates.”

Treasury figures indicate that about half the national debt will mature in the next 70 months. That debt will need to be refinanced as interest rates are rising. The interest rate on outstanding Treasury borrowing averages less than 2 percent.

Moody’s also took issue with Trump’s assertion that faster economic growth will offset tax revenue lost by cutting corporate and individual rates.

“These effects will not be offset by faster economic growth, implying that both the debt burden and debt affordability will erode more quickly” than the Congressional Budget Office estimates, the ratings agency said.

The Friday finish followed Dow’s slide of more than 1,000 points Thursday. On both days, the Dow and the broader S&P 500-stock index crossed the 10 percent threshold from their all-time highs, taking the markets into correction territory for the first time in two years.

Investors around the world are bracing in expectation of more volatility. The broad concern is that inflation would pressure central banks to raise rates, making borrowing more expensive.

“The head winds blowing against markets is monetary tightening,” said Andy Xie, an independent economist in Shanghai. “This kind of yo-yo situation is going to last until the U.S. interest rate rises to a normal level.”

Yang Liu and Luna Lin in Beijing and Paul Schemm contributed to this report.