CHINA'S online search market will breach the 10-billion-yuan (US$1.39 billion) mark in four years to overtake Japan and enter the world's top three.

It means that although the nation's Web population size is set to become the world's No.1 early this year, the commercial value of the huge search market is still to be fully tapped, according to a report by Shanghai-based consultancy iResearch.

"The amount of search inquiries actually has exceeded that of Japan or the United States, but the revenue from each search is far less than those two markets," said iResearch in a report.

Other than the exchange-rate factor, many Chinese corporate users haven't realized the value of "indirect key words" that may lead to visits to their Websites.

Another problem is that most searches are centered on entertainment, among which free movies and music make up the bulk of inquiries.

Search-related ads generated about 2.9 billion yuan last year, according to iResearch, which expects this to expand 76 percent this year and reach 10 billion yuan by the end of 2010. It will definitely surpass Japan in 2011.

As of last year, Beijing-based Baidu.com had the largest share of 60 percent.

Google China ranked second with a share of 21.2 percent as it attracted more customers from real estate, education and healthcare. China Yahoo! finished third last year with a share of 14 percent.