What percentage of the U.S. economy is state run?

Hi, I am wondering what percentage of the U.S. economy is run by the state (the government). Is there any over-arching statistic which gives a good, solid % of how much is run by the state compared to the private sector? I need a source with factual statistics really, not "oh about so and so percent" because I could figure the rough percentage out myself. I am not asking for a school or college paper, just was wondering what the number is. Also, I would be interested in knowing what the % of state run economy is in say China as well, so I can have a good comparison of the U.S. vs. China's public sectors. Thanks.