Fed Daniel Tarullo comments : Tarullo added that some researchers have found that large banks tend to have highly correlated balance sheets, which can in some instances cause systemic effects

WASHINGTON (MarketWatch)
The Dodd-Frank act written in response to the financial crisis complicates the Federal Reserve's review of mergers because it seeks to identify whether such transactions result in increasing risk to financial stability, said Fed Gov. Daniel Tarullo at an event on regulating systemic risk hosted by the central bank.
Tarullo suggested that a review of a merger of two medium sized institutions would need to look at potential increased costs to the system if the combined institution were to fail against the potential benefits of the combined firm having a lesser likelihood of failing.
Tarullo's comments come as the Fed prepares to hold a series of hearings on its review of Capital One Financial Corp.'s  pending acquisition of ING Direct unit of ING
Speaking on the three-year anniversary of Lehman Brothers' bankruptcy, Tarullo added that some researchers have found that large banks tend to have highly correlated balance sheets, which can in some instances cause systemic effects