The five largest banks in the United States reaped tens of billions of dollars in profits in the first half of the year, thanks in part to a strong economy and to the lingering effects of President Trump’s tax cuts.

Bank of America, Citigroup, Goldman Sachs, JPMorgan Chase and Wells Fargo have all seen their tax rates decline to 22 percent or less as a result of the cuts, compared with rates of around 30 percent three years ago, one of the most consistent sources of strength apparent in quarterly earnings reports issued this week.

JPMorgan’s tax rate fell to just under 15 percent in this year’s second quarter, although the bank said it would probably inch higher later in the year. Wells Fargo’s tax rate for the quarter was just over 17 percent, and Bank of America’s was 18 percent.

The reduced rates helped offset a general decline in Wall Street trading revenue and added some pep to what would have otherwise been unremarkable quarterly performances by most of the banks.