Market research firm eMarketer has said that China is poised to become the largest online ad market in Asia-Pacific by 2015.

This year, eMarketer says, total advertisment spending in China will increase significantly to make the country the second-largest advertising market in the world.

The market research company said that by the end of this year, spending in China will increase by 14% in 2011, to $38.3bn to displace Japan, where total media ad spending last year reached $34bn.

The company said that this year ad spending in Japan is expected to drop by 3.7%, to $32.7bn after slow, 0.4% growth in spending last year, and the effect of the tsunami and continuing economic difficulties.

According to eMarketer, the US will remain the world’s leading country in terms of total media ad spending, with a projected $157.4bn in ad dollars this year.

eMarketer director of strategic communications and author of the new report, "Worldwide Ad Spending: Online Drives Growth." Kris Oser said one key reason for Asia-Pacific’s growth in ad spending is that the region’s two most populous countries — India and China — also boast two of the world’s fastest-growing economies.

"In 2010, China surpassed Japan as the world’s second-biggest economy. And this year marks another major milestone for the country."

However, online, China still has some catching up to do, said eMarketer. This year, eMarketer estimates, advertisers will spend $4.6bn on digital in the country, far short of Japan’s projected $7.2bn in spending.

But by 2014, China’s higher growth trajectory will bring the two countries even with each other, at $9.5bn in spending.

The following year, China will win out and become the largest online ad market in Asia-Pacific.