The shares of big banks like JPMorgan Chase & Co. (JPM) - Get Report , Bank of America Corp. (BAC) - Get Report and Citigroup Inc. (C) - Get Report could tumble by 20% if the U.S. economy slips into recession, Goldman Sachs estimated in a report on Monday, Jan. 7. 

While the Goldman analysts led by Richard Ramsden wrote that they don't expect a recession, the current pricing of the bank stocks only reflects roughly half of the earnings-per-share decline that could come from elevated loan losses, shrinking lending margins, zero loan growth, tumbling trading revenue and a drop in asset-management fees. 

Earnings per share would drop by an average of roughly 45% in 2020 across seven large banks, according to the analysts. 

"Roughly 50% of this scenario appears priced in," according to the Goldman report. 

As recently as June, JPMorgan CEO Jamie Dimon had asserted that the banking industry was enjoying a "golden age," thanks partly to Federal Reserve interest-rate increases that fattened lending margins -- since most of the large banks continued paying next to nothing to savers with deposit accounts.  

But U.S. stocks fell last year by the most in a decade, with the Standard & Poor's 500 Index down 6.2%, as traders became increasingly jittery that the economy was slowing, especially with the economic stimulus fading from President Donald Trump's tax cuts passed in late 2017. The U.S. economy is already in its 10th year of expansion, approaching the longest on record. 

On average, economists still expect positive economic growth in the next three years, albeit slowing to 2.5% this year from an estimated 2.9% in 2018. 

Even so, market signals such as the recent decline in stocks and a shrinking gap between yields on short-term and long-term U.S. Treasury bonds have prompted some analysts to speculate that a recession could happen as soon as this year. 

The banks likely would remain profitable in a recession, the Goldman analysts wrote, though losses could swell if it's longer or deeper than usual.    

"Given the slower nature of this economic recovery, as well as less pronounced asset bubbles at this stage, we see this outcome as a remote possibility," according to the report.