From International Outlook magazine visa sina.com (in Chinese), translated by CDT (link):
Although the Chinese government has been publishing a national defense white paper and data about its military spending, many western countries, including the United States and Japan, generally don’t buy the credibility of the papers and figures. A recent report released by the Pentagon about China’s military buildup accuses the lack of transparency of China’s information releasing and says the China’s actual military spending is two or three times the Chinese government pronounces.
Since the reform and opening up in late 1970s, China started releasing military spending and other formerly classified information. A lot of information about Chinese military, however, remained undisclosed. One of the bases of not going transparent was a remark by Yang Shangkun, former vice chairman of the powerful central military commission, who turned down a request of visit to Chinese nuclear submarines in 1980s by an American submarine expert. “Our submarines are indeed lagging behind those of the US, but we cannot let them know how much we are behind them,” Yang said.
The major difference of western perspective on Chinese military is the different definition of “defense spending.” The items listed in China’s defense white papers are “military spending,” not including expenditures of dual-use technology agencies or companies, armed police or other reservist personnel, among other things. Taiwanese media criticized its government for not listing spending by Academia Sinica in weapons development, which will boost Taiwan’s defense spending by 30-40 percent.
Even add up the spendings for armed police, reservist forces and research for dual-use technologies, China’s military spending will be at most several tenths more, definitely not three times of the disclosed figure.