Not surprised at all. China 2015 GDP could be 2 to 3 times

higher than the US counterpart, reaching US$35 to $50 trillion. Otherwise, it is impossible to explain the actual economic scale in China. Give you a simple example how this figure is estimated. During the spring festival month, ~6 billion people/time were transported from place A to B by the transportation systems (e.g., high speed rails, express ways) in China. Only China has such ability to do such activities. Assuming a person spent US$1000 this month, that would create US$6 trillion GDP. Remember this is only a month!

Over 30 million automobiles were produced in China in the same year. Plus, ~800 million tons of steel were produced in that China, accounding for ~55% of the steel production of the world! 

China does have property tax. Given that was counted, that would create about US$2 trillion GDP.