The five largest U.S. investment banks generated strong quarterly net revenues and earnings despite adverse conditions stemming from the domestic residential mortgage market, according to a new report from Fitch Ratings.

Fitch attributes the positive results to four factors: effective product diversity, tempering the affect of the deteriorating subprime mortgage market; active employment of hedges to limit their credit and interest rate risks from real estate collateral owned or warehoused; increasing geographic diversity; and, sufficient capital to support underperforming and deteriorating assets, avoiding the need for ‘fire sales’ that would pressure some values and exacerbate negative mark-to-market adjustments.

“While mortgage exposure exists throughout investment banks’ franchises, each firm says that fewer than 5% of total net revenues are attributable to subprime mortgage activities,” said Leslie Bright, senior director, Fitch Ratings. “Since May, unusual levels of credit deterioration have been concentrated in the subprime space, impacting underwriting and primary trading markets. Contagion to the Alt-A and prime sectors has greater possibility, as does fallout in the secondary market following pending rate resets of vintage mortgage pools.”

Fitch notes that balance sheet valuations will be a primary factor in future operating results, impacting both the market and credit risks of these firms. On the asset side, fair value reporting will require downward adjustments in several asset categories that hold mortgage-backed and other financial instruments under pressure, including: resales, trading assets, investment securities and mortgages that decline in value. On the liability side, repos and trading liabilities could be impacted, it says.

“The U.S. firms were able to seize opportunities in the capital markets to produce substantial, sometimes record-level revenues, for advisory, underwriting and distribution services. The consolidated results also reflected the benefits of product and geographical diversification within each franchise that resulted in solid contributions from core businesses,” Bright said.