Following a report earlier today that iTunes has become the second-largest music retailer in the US, an NPD executive has said that the store will likely knock Wal-Mart from the top spot later this year. “Digital sales were up close to 50 percent and CD sales were down 20 percent last year,” said Russ Crupnik, president of music for the NPD Group. “Even at half that growth rate in digital sales, Apple will in all likelihood catch…
