This is because in the domestic version of the model is generally relatively new. This is because the per capita income in the United States is $4,000, while the price of an Apple phone in the United States is only about $1,000. Therefore, the frequency of Americans to change their mobile phones is much greater than that of domestic users, and many American users sell their mobile phones directly after they feel bad for a few days, after all, their wages can buy several of the latest Apple mobile phones.