Still, the recent plight of bank stocks does not bode well.

On Monday, shares of Deutsche Bank, Germany’s largest bank, plummeted nearly 10 percent in Frankfurt, while those in Standard Chartered, a British bank, fell nearly 6 percent, and stock in Citigroup declined more than 5 percent.

Deutsche Bank and a handful of other European banks are contending with their own problems that could explain the depth of their recent declines. Banks issue debt to raise money for their loans and operations. In recent weeks, investors have paid a higher price to buy insurance against a bank defaulting on such debt. The cost of using so-called credit-default swaps to gain protection for five years on Deutsche Bank’s debt has doubled since the start of this year, according to data from Markit.

Outside of Europe, though, the moves in bank shares are hardly reassuring.

Citigroup’s shares, for instance, are down by more than a fourth so far this year. And its stock trades at nearly half of the bank’s book value, which is a theoretical measure of the value that would be left for shareholders if the bank were liquidated. The discount to book value exists at other large banks and effectively indicates that investors have doubts about the banks’ ability to earn a strong return on their capital.

Still, Citigroup made over $17 billion in profits last year, has stable management and, looking at its balance sheet, possesses the financial strength to weather an economic slowdown.

There is a good chance that investors have become too pessimistic about the big banks’ prospects, and their stocks could bounce back if the wider funk in the market passes. Most banks, after all, are substantially stronger than they were in 2008. And, since then, the banks have managed to earn profits even as they have dealt with a barrage of government lawsuits as well as economic and financial turbulence in Europe and Asia.

Still, the declines in bank shares may not indicate that banks are particularly fragile right now but that investors think they will struggle to earn solid profits in the future, at least in part because of ultralow interest rates around the world.

Central banks have kept interest rates low to stimulate demand for loans. But loans with low interest rates are often less profitable for banks. As a result, banks may then lend less, which may then reduce the overall impact of low interest rates on the economy.