A sell-off in markets around the world turned into a rout on Monday as investors grew panicky about signs of a slowing American economy, with stocks tumbling across Asia and Europe.
The moves were a sharp reversal in the world’s major markets, which for much of the past year have risen to new heights, propelled by optimism about cooling inflation, solid labor markets and the promise of artificial intelligence technology.
The declines were especially pronounced in Japan, where fears about the economy added to other concerns about the damage a strengthening yen could do to corporate profits.
The Nikkei 225 index fell 12.4 percent. It was the benchmark index’s biggest one-day point decline, larger than the plunge during the Black Monday stock market crash in October 1987. The Topix index, which includes companies that represent a broad swath of Japan’s economy, fell 12.2 percent.
The unease spread to Europe, where the Pan-European Stoxx index fell more than 2 percent in early trading, with every major market on the continent recording declines.
The losses were set to continue in the United States. Stock futures for the S&P 500 were down more than 2 percent, and those for the Nasdaq fell more than 4 percent.