Sometimes trading desks get banks into trouble – and sometimes they keep them out of it. As U.S. lenders put aside billions of dollars to cover bad loans amid an economic slump, it’s those with armies of traders which can cover the resulting losses. In the second quarter of 2020, JPMorgan (JPM) had the best of all worlds, and Wells Fargo (WFC) had the worst.

Jamie Dimon’s $300 billion bank put aside $8.9 billion of reserves to cover soured loans in the three months to the end of June, as it plans for rising delinquencies. Roughly 7% of its mortgage and car-loan customers are already receiving forbearance. The resulting provisions drove JPMorgan’s colossal retail and commercial banks to a combined loss of almost $870 million. It’s a similar story at Citigroup (C), whose North America consumer bank bled red ink thanks to a firm-wide $5.5 billion provision.

It was trading and investment banking that made up the difference, and then some. The market’s wild ride doubled JPMorgan’s fixed-income revenue compared to last year’s second-quarter showing, and fees from underwriting stock and bond issues increased around 70%. At a time when millions of Americans are unable to pay their rent, JPMorgan’s near-$10 billion of trading revenue marked its best quarter ever.

Wells Fargo is in a different situation. The $100 billion San Francisco-based bank has little in the way of trading, but like everyone, is having to lay aside provisions to cover bad loans. The $8.4 billion the lender set aside drove it to a $2.4 billion quarterly loss – only its third this century. And with 2.2% of its loans now provided for, it’s still slightly less well upholstered than JPMorgan. Chief Executive Charlie Scharf also slashed Wells Fargo’s dividend. Investors can only hope this is his version of a “big bath.”

Another thing that divides winners and losers is how well they have kept costs down. JPMorgan’s expenses account for just half of its revenue, meaning it had $17 billion of profit from which to cover its provisions. Citi is similarly lean. But partly because expenses are already 82% of its revenue, Wells Fargo made a meager $3.3 billion from which to pad against bad debt. Traders may have bailed some banks out, but not everyone started off in the same-sized hole.