As recently as 2010, growth in US Facebook usage was well into the double digits, at 38.6%, eMarketer estimates. But with 116.8 million US internet users already logging on to the site at least once monthly that year, growth rates were bound to plateau.
By 2011 Facebook user growth rose a comparatively small 13.4%, and this year will be the first when growth rates drop to the single digits. Rates of change in the US will continue to decline throughout eMarketer’s forecast period.
On Twitter, by contrast, growth is stronger. Last year’s 31.9% increase in users outpaced that of 2010, when growth was at 23.5%. Similar to Facebook’s trajectory, Twitter’s growth rate will also fall in the coming years, but still remain nearly four times higher than Facebook’s growth rate in 2014.
Twitter’s size, which is fairly small, is one factor that makes such growth rates possible. Facebook already reached an enormous audience of nearly 133 million US internet users at the end of 2011, a figure that will surpass 150 million by 2014. Twitter, in comparison, had a US user base of less than 24 million at the end of last year. Still, between 2010 and 2014, eMarketer predicts, Twitter will about double its US user base, reaching 37.6 million microbloggers by the period’s end.