"Subramaniam's paper points out that the change in the data sources and methodology for the estimation of real Gross Domestic Product since 2011–2012 has led to a significant overestimation of the growth estimates. The actual growth between 2011 and 2017 is estimated at around 7 percent as per the official sources. However, according to Subramanian, the actual growth may have been only around 4.5 percent. A part of this overestimation according to the paper may be attributed to a key methodological change.
Earlier this year, a study reported that China’s economy is about 12 percent smaller than the official figures, and also that the real growth has been exaggerated by about 1.7 percent annually from 2008–2016.
The study was published in the Brookings papers of economic activity by a team of economists namely; Wei Chen, Xilu Chen, Chang-Tai Hsieh, and Zheng (Michael) Song: "China’s National Bureau of Statistics (NBS) adjusts the data provided by local governments to calculate GDP at the national level. The adjustments made by the NBS average 5% of GDP since the mid-2000s.""