On the same day a merchant group's study claimed retailers pass on interchange savings to consumers,debit card issuers released their own study that claims merchantsdo no such thing.

“As part of their lobbying tactics, giant retailers promised tolower prices for their customers if Congress passed the Durbinamendment. Two years after implementation, retailers have takenhome an $8 billion annual windfall while their customers stillaren't seeing a discount for using debit,” said Sam Fabens,spokesman for the Electronic Payments Coalition, which sponsored the study.

To collect the data for the field research, 32 shopping tripswere performed at 16 stores nationwide. Identical products werepurchased at each store and compared: one shopping trip inSeptember 2011 before implementation of the Durbin amendment; onein September 2012 – a year after the implementation of the Durbinamendment; and one in September 2013 – two years after theimplementation of the Durbin amendment.

This differs sharply from the merchant study, also released onTuesday, which said merchants use their interchange savings tolower prices by applying a previous study of merchant behavior tothe known amount of interchange savings released by the FederalReserve.

Specific findings included that the price of milk at a Walgreensin San Francisco has increased by 30 cents in the past year, andthe cost of peanut butter at a 7-Eleven in Boston went up by 20cents.

The research shoppers found a hammer at a Home Depot inPortland, Maine, had been $4.98 since before the implementation ofthe Durbin amendment in 2011 and that a Slurpee from a 7-Eleven inWashington, D.C., has cost $1.49 each year since 2011.

Finally, the cost of macaroni and cheese from a Wal-Mart inWashington, D.C., has been $1.38 every year since 2011 while thecost of paint from a Home Depot in Atlanta has stayed the sameprice since last year, the EPC study found.