Marketing research firm eMarketer has released its first-ever forecast of Twitter users worldwide, and projects that the social network will have nearly 400 million users by 2018, with over 40 percent of them in the Asia-Pacific region.

By the end of this year alone, the Asia-Pacific region will account for 32.8 percent of all Twitter users, exceeding its 23.7 percent share in North America, according to eMarketer’s estimates. This is despite a ban on the social networking site in China, which has one of the region’s largest portion of internet users. eMarketer notes that if China opens up to Twitter before 2018, the share of its users in the region “is likely to be significantly higher.”

India and Indonesia are strong-performing markets for Twitter, according to eMarketer. Both countries will see user numbers increase by more than 50 percent this year, becoming the third and fourth-largest Twitter populations, projected at 18.1 million and 15.3 million users respectively. This will see it pass the UK for the first time this year, eMarketer notes.

Interestingly enough, eMarketer’s estimates pin Twitter’s monthly active users at 183 million in 2013. This is some way off from Twitter’s reported figure of 241 million monthly active users at the end of last year, as eMarketer says it processes consumer survey data to “weed out business accounts, multiple accounts for individual users and other sources of potential double-counting.”

eMarketer’s forecast shows that Twitter’s user base will increase 24.4 percent this year. It also predicts that the increment in the number of Twitter’s monthly active users will slow over the years of its forecast period, but still rack up double-digit growth rates throughout.

eMarketer Twitter Research projects that Twitter will hit nearly 400m users by 2018, with over 40% in Asia Pacific

Meanwhile, eMarketer notes that Twitter’s growth in the US is maturing, and gains in the country will slow to single digits by 2015. The US will still remain the single largest country in terms of number of individual Twitter users throughout eMarketer’s forecast period, it says, but its market share will decline over the years, which should be enough impetus for the social networking site to grow its non-US ad revenues by “leveraging an expanding user base in emerging markets.”

Even though Twitter accounts outside the US made up 77 percent of the social network’s average monthly active users in the three months ended June 30, 2013, international revenue was only 25 percent of its consolidated total for the same period. Shailesh Rao, Twitter’s vice president of Americas, Asia Pacific and emerging markets, told us previously in an interview that this means huge opportunities for the company and he’s extremely bullish about the future of Twitter advertising in the Asia-Pacific region.

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