Who has the right figures on China's ad spending?

China lacks good metrics. It became very clear again with the recent overviews of the 2006 advertising spendings. In February 2007 Nielsen Media Research claimed that China's advertising expenditure via television, newspapers and magazines reached 386.6 billion yuan - US$ 49.5 billion- in 2006. Which was up 22 percent on the previous year. In their figures TV held a 81% market share.
This week a competitor of them (CTR) launched their figures: US$ 36.9 billion. Which is an annual growth of 18%. TV takes a 76% market share.
This US$ 13 billion difference between the two top researchers is really huge. Can anyone explain me the reason? May be the figures of CTR are right since their majority shareholder is CITV, the commercial arm of the state owned CCTV.
Both only agree that China ranks now the third in the global advertising market - together with the UK- after the US and Japan But these 3 markets grow slowly (US + 3.8%) or have negative growth (Japan - 0.2% and UK - 1.8%). Growth potential in China remains huge since advertising spending accounted for only 1.4% of GDP versus 3% in the US.
None of them mentions the web as channel. I even don't think they measure the web. It again illustrates the claims I made earlier on on the irrational overspending in TV.    

Read also Fons Tuinstra's comments on my naive search for the right figures.