The Economic Information Daily tallied up gross domestic product (GDP) data from 28 of mainland China's 31 provincial-level authorities, totalling 42.4 trillion yuan for the first nine months of the year.
But the figure for the whole country, already announced by Beijing, is 3.7 trillion yuan lower.
The discrepancy which has been in place for more than two decades has been widening rapidly in recent years, the Economic Information Daily said.
"Some regions may have inflated the statistics due to their distorted perception of achievements given the fact that the performance assessment of local governments is often linked with GDP growth," the report quoted an unnamed National Bureau of Statistics official as saying.
China's Premier Li Keqiang said in 2007, when he was the governor of Liaoning province, that some Chinese data was "man-made", according to a confidential memo released by the WikiLeaks website in 2010.
Chinese President Xi Jinping said in June that officials' performance evaluations must not be based "simply on GDP growth rate" but take into account factors such as the environment and improving people's well-being.
