China began catching up to the U.S. late last year and as of January 2013, the two countries had approximately the same smart device user base, with 222 million in the United States and 221 million in China.
Based on the number of devices per country in the first half of February and growth trends, Flurry predicts that by the end of February 2013, China will outpace the U.S. by a wider margin with 246 million devices compared to 230 million in the United States. China is expected to retain that lead due to population numbers.
The U.S. and China have a huge number of active smart devices compared to other countries, with almost five times more devices than the U.K, which represents the third largest smart device market. As of January 2013, the U.K. had 43 million smart devices. South Korea and Japan are the fourth and fifth largest markets, with 30 and 29 million respectively.
China in particular has experienced rapid growth, adding 150 million devices during the course of 2012, compared to 55 million new devices in the U.S.
During Apple's quarterly results call this January, the company reported a 67 percent increase in revenue in China, amounting to $6.8 billion during the first fiscal quarter of 2013.
China has become an increasingly important market for Apple, as its second largest region. CEO Tim Cook spent part of January in the country, where he emphasized Apple's plans to expand in the country.