Muddled is the word when it comes to trying to quantify the costs that banks have incurred complying with the Dodd-Frank Act.

Trade associations representing the financial services industry often cite high compliance costs as a reason the 2010 law needs to be rolled back.

But none of the nine largest American banks currently designated as “systemically important financial institutions,” or SIFIs, could provide Bloomberg BNA details on what it cost them to implement the 2010 law.

What data is available related to Dodd-Frank compliance costs provides an inconsistent picture about whether banks are burdened by the rule....