Profits have soared since the global financial crisis at the five biggest U.S. banks with market-making dealing operations, New York Federal Reserve economists said in an article released on Wednesday.

From 2009 to 2014, the combined net income of J.P. Morgan, Citigroup, Bank of America, Goldman Sachs and Morgan Stanley annually averaged $41.73 billion, up from annual average of $25.08 billion from 2002 to 2008, they said.

Helping boost profits were trading revenues that they and other dealers have seen returning to the levels before the financial crisis seven years ago.

Their annual income was also more stable than pre-crisis levels, they added.

There have been concerns tighter regulations have caused significant cutback in dealers' market-making activities, resulting in a decline in market liquidity and "flash" events including the one seen nearly a year ago in the Treasuries market.

"These trading revenue and income figures suggest that dealers continue to play a key role in liquidity provision," New York Fed economists Tobias Adrian, Michael Fleming, Or Shachar, Daniel Stackman and Erik Vogt wrote in their blog titled "Changes in the Returns to Market Making."

The banks' "Sharpe ratio" on their income rose to 2.28 from 1.23, suggesting milder swings in their annual earnings since the global credit crunch.