Wage statistics are one of China's "dim sums" that don't reflect reality. Farmer's Daily says The National Bureau of Statistics announced that it will begin to include private firms and small businesses in its survey of wage statistics.
Current statistics are based on surveys that include only government, quasi-government service units, state-owned and collective enterprises. In 2008, the average urban salary was reported as 29,299 yuan, but a survey of private enterprises found their average was just 17,071 yuan, 58% of the reported average. The statistics clearly don't reflect actual earnings of "the masses."
The former survey only covered 110 million urban employed persons. At the end of 2008, it was estimated by NBS that private enterprises employed 66.76 million. It is estimated that there are 50 million small merchants (ge ti hu).
The change is being made partly because the common people ("old hundred names") don't believe official statistics since they don't reflect their low salaries. The article says statistics have been improved a lot in recent years to take into account a broader segment of society and better reflect actual earnings, macroeconomic conditions, and living standards. But there is still room for improvement.