Trading revenue for U.S. banks dropped by about 20% in the fourth quarter, according to report from the U.S. Office of the Comptroller of the Currency (OCC) published on Wednesday.

Trading revenue for U.S. commercial banks and savings associations fell to US$4.3 billion in the fourth quarter of 2015, according to the report, down from US$5.3 billion in the previous quarter. While much of the drop reflects seasonal factors, revenue was also down by 4% from the same period in 2014, the report notes.

Trading risk exposure, as measured by average value-at-risk (VaR), decreased in the fourth quarter of 2015.

Banks’ derivatives holdings declined by US$11 trillion in the fourth quarter to US$181 trillion. “The decline results from industry efforts to eliminate offsetting trades, an activity known as trade compression, rather than a significant reduction in the volume of trading activity,” the report says.