The nascent, yet fast growing market for mobile payment services received a boost on Wednesday as 14 major retailers announced plans to develop jointly a mobile payments network that will enable customers to complete purchases via their wireless smart phones. Christened the Merchant Customer Exchange (MCX), the initiative includes retail giants Wal-Mart and Target, Best Buy, Sears, 7-Eleven, Inc., Sunoco, and other grocery, gasoline and drug store chains. The venture adds to a growing list of mobile payment rivals that already includes Isis (a strategic partnership among AT&T, Verizon Wireless, and T-Mobile USA), Google’s Android-based Wallet service, and start-up venture Square, Inc. which said last week it would invest $25 million to process mobile debit and credit transactions at Starbucks coffee outlets throughout the U.S. By downloading mobile payment applications onto their smart phones, customers can complete purchases by tapping their handsets against specially designed readers positioned by the cash register. A recent report from Juniper Research forecasts explosive growth in the mobile payment market, in which total transactions are expected to quadruple to more than $1.3 billion annually by 2017. Although a launch date has yet to be announced for MCX, Terry Scully, the president of financial and retail services at Target, stressed that the goal of the venture is to achieve “a broad, seamless experience across all retail formats.”