The S&P 500 fell 1.4% on Thursday, marking its lowest point of the year and sliding into a market correction, as it is now down 10.1% from the all-time high it reached less than a month ago. The Dow Jones Industrial Average also hit a year-to-date low, closing down 537 points.

President Donald Trump in recent days has dismissed fears of a recession and brushed aside the stock market sell-off, going so far as to say, “You can’t really watch the stock market.”

Stocks have plunged in amid fears that tariffs will weigh on economic growth. Yet, there may be a more under-the-radar reason behind the sell-off.