Santa’s sleigh is usually pulled by reindeer. This year, it looks as if it will be pulled by a team of bears.

The Nasdaq Composite tumbled 8.4%, to 6332.99 last week—its largest drop since 2008—ending down 22% from its August high and placing it firmly in bear-market territory. The Dow Jones Industrial Average dropped 6.9%, to 22445.37, while the S&P 500 slumped 7.1%, to 2416.58, leaving them down 16% and 18%, respectively, from their all-time highs. No one would be surprised if they entered bear markets of their own before the end of the year.

What’s striking is how quickly we’ve come to this point. Entering December, all three indexes were in positive territory for the year. Now, the Dow, down 12% this month, is on pace for its worst December since 1931. While government shutdowns and cabinet resignations make for good headlines, there is only one thing that gets the market to slide like that: recession fears, in this case exacerbated by a Federal Reserve that seems reluctant to acknowledge that possibility.

The odds of a recession have increased. Jason Pride, chief investment officer of private wealth at Glenmede, puts the chances of a slowdown at about 35%, and while that means there’s a 65% chance that a downturn is avoided, those are “not gambler’s odds,” he says, referring to what a pro would require to make a bet. What’s more, when the odds of a slump are that high, it signals a high level of fragility in the economy, which means that an accident—whether from the Fed, the White House, or something we haven’t even imagined yet—could “come out of left field and knock this economy into recession,” Pride says.