An estimated 1.61 billion people, or 1 in 5 globally, will log in to social networking sites at least monthly, according to research agency eMarketer.
The number was up 14.2 percent from a year ago and growth will push that number up to 2.33 billion by 2017, according to its study on Tuesday.
The fastest growth in social network usage is happening in less-developed markets, noted eMarketer, with India leading. The country saw user numbers increase by 37.4 percent, ahead of Indonesia at 28.7 percent and Mexico by 21.1 percent.
All three of those countries are also high-growth areas for Facebook, which eMarketer estimates will reach a worldwide monthly user base of 1.026 billion this year. In terms of Facebook uers, India is a distant second behind the U.S. which currently has 146.8 million members. However eMarketer believes India is set to overtake U.S. to become the largest Facebook population by 2016.
India's social network penetration currently stands at only 7.7 percent, below the average of 22.7 percent worldwide.
On the other end of the scale, the Netherlands was the most socially-connected country with a penetration rate of 63.5 percent. Norway follows just behind at 63.3 percent, and Sweden at 56.4 percent.