The Federal Reserve Bank of Richmond reveals less than 10% of merchants saved on debit costs post-Durbin.
Federal Reserve says fraud prevention adjustment costs should remain part of the equation.
The court order is the latest development in a lawsuit filed by retailers nearly two years ago.
Mercator Advisory Group finds 50-60% of financial institutions offer debit rewards.
Sen. Dick Durbin (D-Ill.) files an amicus brief with the Supreme Court, arguing for a lower Fed interchange cap.
Retail trade associations and two large retailers appeal to the Supreme Court to rule on the Federal Reserve's debit interchange rule.
National Retail Federation and other groups attacked the amount of debit card interchange allowed.
Retail trade associations and firms call the Fed's debit interchange rule an issue of staggering importance.
A Friday ruling allows retailers who opted out of last year's settlement to proceed with new suits. Card brands can also countersue retailers.
A new Aité Group report says cash is more expensive for retailers than cards. Retailer groups disagree.