Recent losses on global financial markets, including those in the U.S., have some investors concerned about expectations for their holdings and plans for the future.
The Dow Jones Industrial Average declined 2.5 percent Friday, its largest percentage drop since Britain's decision in June 2016 to leave the European Union.
The Dow and the broader U.S. Standard & Poor's 500 Index ended the week roughly 4-percent lower, their biggest weekly drops since early 2016, amid fears of inflation and disappointing quarterly corporate earnings results.
Key stock indexes in Europe also fell Friday. Germany's DAX index dropped 1.7-percent, while France's CAC 40 Index declined 1.6-percent.
In Asia, Japan's Nikkei 225 Index slid nearly 1-percent and South Korea's Kospi fell 1.7-percent.
Meanwhile, U.S. bond yields climbed and contributed to the sell-off after the U.S. government reported that wages grew last month at their fastest pace in eight years.
The wage data helped stoke investor concern that the Federal Reserve, the U.S. central bank, will respond to higher inflation by hiking its key interest rate more quickly than anticipated.
Darrell Cronk, head of the Wells Fargo Investment Institute, said an extended period of low interest rates has helped create the uncertainty.
"We've enjoyed low interest rates for so long, we're having to deal with a little bit higher rates now, so the market is trying to figure out what that could mean for inflation.''
The yield on the benchmark 10-year U.S. Treasury notes rose to 2.852-percent, its highest level in more than four years. The rise in bond yields hinders stock performance in two ways: it makes corporate borrowing more expensive and it makes bonds more attractive to investors compared to riskier stocks.
Bond strategists were unwilling Friday to predict what lies ahead for interest rates this week after the markets' unusual volatility in the past week.
Investors may get a hint of the direction of interest rates when trading resumes in Asia early Monday, and possibly more insight after the U.S. Treasury's $66 billion in auctions of 3-, 10- and 30-year bonds from Tuesday to Thursday.