The mobile game market is definitely booming especially in China, with free-to-play games and other titles getting plenty of attention.

A new report from GamesIndustry International suggests that the popularity of mobile games may be bigger than expected, as domestic revenue is set to eclipse similar numbers in the United States.

Based on numbers provided by Niko Partners, domestic mobile game revenue in China will reach $5.5 billion this year. That’s a $2.2 billion increase from numbers reported last year, indicating that the mobile market is bigger than ever overseas.

SuperData also chimed in with its own numbers, stating that revenue from the U.S. mobile game market will reach $4.5 billion for this year. That’s still big, but obviously the USA is not the leading country anymore. That gap could continue to grow, especially with China’s large population.

Niko indicates that the number of Chinese mobile gamers will reach a whopping 420 million by year’s end, a jump over the 366 million reported for the first half of the year. In addition, revenue could reach an even higher stat in just a few years’ time, estimated to reach $11.1 billion by 2019.

Tencent seems to be the leading source of mobile entertainment in China, with a 50 percent market share of the overall mobile outreach for last year. While more foreign companies are hopping on board (including a few Western developers), Niko Partners suggests using a little caution. “It is important to evaluate what voids there are in Chinese culture, and then match game development to those as well as to the gamer behavior and characteristics of a good mobile game in a popular genre,” said Lisa Cosmas Hanson, managing partner and founder of Niko Partners, in a statement.

“With that mobile game developers may find their way to the next big Chinese hit game, because hoping to make it big with an international title lobbed to a Chinese publisher for localization is not an effective path to success.”