In a letter to Apple investors on January 2, Apple CEO Tim Cook warned that the company’s revenues for the fourth quarter would be lower than expected. He blamed the shortfall on the “magnitude of the economic deceleration particularly in Greater China.” But China’s slowing economy and a burgeoning trade war with the U.S. are not the only factors responsible for Apple’s troubles in China, writes Wharton professor of operations, information and decisions Kartik Hosanagar in this opinion piece. A slew of Chinese rivals has gradually eroded the iPhone’s once dominant market share in the country, he notes. Hosanagar joined Jyoti Thottam, business and economics editor in the Opinion section of The New York Times , on the Knowledge at Wharton radio show on Sirius XM to discuss Apple’s problems and what they reveal about the prospects of other U.S. companies that depend significantly on China for revenues. “Most of Apple’s troubles in China are related to factors other than the trade war,” he said.…