China, with nearly 1.3 billion people, started doubling its economy every 10 years or less, starting around 21 years before 2011.

True: China's population was about 1.3 billion around 2011 (official figures within about 5%). Also, real GDP grew enough to double every 10 years or less, meaning average growth of at least about 7.2% a year, from around 1990 (give or take a few years) to 2011. Mostly true: the growth claim holds, but the population figure is slightly off (e.g., 1.34 billion described as 'nearly 1.3 billion'), or the start date differs by several years. Mixed: growth reached the doubling pace for only part of the period. Mostly false: average growth fell clearly short of about 7% a year over the period. False: growth was far below the doubling pace, or the population figure is wildly wrong.

Set before the research began.

1. E1 Press Release on Major Figures of the 2010 National Population Census National Bureau of Statistics of China (Ma Jiantang, Commissioner) · 28 April 2011

   “Total population as was enumerated through the census was 1,339,724,852 persons, an increase of 73.90 million persons or 5.84 percent over the 10 years since the 2000 census”

2. E2 Impact of Trading Gains on Economic Growth in BRICs for 1995-2010: Some Lessons from BRICs Russian Research Center, Institute of Economic Research, Hitotsubashi University (Masaaki Kuboniwa) · May 2011

   “Figure 2 shows BRIC growth for the extended period 1990-2010. China and India grew fastest over this interval with the average 10.4 percent and 6.6 percent respectively.”

3. E3 China and the Global Economy World Bank (Justin Yifu Lin)

   “But China's annual growth rate during the period 1990-2010 increased to 10.4 percent.”

4. E4 How to sustain the Chinese economic miracle? The risk of unraveling the global rebalancing Levy Economics Institute of Bard College (Jörg Bibow), Working Paper No. 617 · 2010

   “With a population of 1.33bn and labor force of 800 million (in 2008), China is far advanced in its demographic transition”

E2 and E3 each report China's average real growth for 1990–2010 as 10.4% a year. That is well above the roughly 7.2% needed to double every 10 years, so the growth part of the claim holds. E1 gives the 2010 census population as about 1.34 billion, and E4 gives 1.33 billion for 2008. Both are within 5% of 1.3 billion, but the criteria name 1.34 billion described as 'nearly 1.3 billion' as their example of a mostly-true case.