MasterCard Inc will lose more than half of a $59 billion portfolio of U.S. debit card users to Visa Inc after JPMorgan Chase & Co shifted more business to its rival, people familiar with the matter told Bloomberg.

MasterCard had held the portfolio since 2005, the people said, requesting anonymity because the move had not been officially announced.

The debit card users in question held accounts at Washington Mutual Inc until JPMorgan bought the assets of that failed lender last year while bidding for the accounts began in October, the people said, according to the report.

A spokeswoman said “decisions such as these can occur” due to the competitive nature of the industry,” Bloomberg reported. Some business of the debit business will remain with MasterCard the spokeswoman said.