• by Erik Sass , Staff Writer @eriksass1, August 12, 2010

A new report from eMarketer documents the incredibly rapid growth in social networks over the last couple years, and predicts continuing growth at least into the middle years of this decade -- but also suggests that social networks may be approaching saturation in the U.S. According to eMarketer, the number of Americans who checked into a social network at least once a month increased by 24.7 million from 2008-2009, from 84.5 million to 109.2 million -- representing an increase from 41.6% to 51.6% of the total population. This year, eMarketer expects 17.8 million more people to sign on, bringing the proportion to 57.5% of the total population, followed by another 13.2 million in 2011, 10.2 million in 2012, 7.5 million in 2013, and 7 million in 2014, when a total 164.9 million Americans will check in to a social network at least once a month, representing 65.8% of the population.

There's no question this would represent a slowing in the rate of growth: from 2008-2014, the year-over-year percentage growth rate would decrease from 29.2% to just 4.4%. This forecast isn't really surprising, considering that the growth rate in the overall U.S. Internet population is also slowing; according to Pew, the proportion of Americans with broadband access at home edged up from 63% in 2009 to 66% in 2010 -- a 3% increase, compared to the 8% increase from 2008-2009.

So how can social networks to continue growing? In the short term, this will require breaking through to previously untapped or underrepresented populations.

One obvious under-utilizing group is adults over 65, who currently make up 18% of the total U.S. adult population according to the U.S. Census Bureau, but just 3% of the U.S. social network population, according to an analysis from Pingdom.com. There are some clear challenges, as the group lags in Internet usage in general, but also significant opportunities: Pew found that the proportion of Americans ages 70-75 who were online increased from 26% in 2005 to 45% in 2009. Taking a (much) longer view, even if social networks can't recruit more members from this group right now, the proportion of older people on social networks will rise naturally, as people currently in their 40s and 50s who are members continue to participate in their retirement years.

Returning to the short term, there is room for more immediate growth among certain ethnic groups: at the end of 2009, Facebook stats showed that 9% of its U.S. members were Latino, compared to 16% of the population at large; similarly, 11% were African-Americans, compared to 13.5% of the general population. The proportion of Latinos and African-Americans using the Internet continues to increase (the proportion of Latino adults using the Internet increased from 54% to 64% from 2006-2008, according to Pew, which also said the proportion of African-American households with broadband Web access increased from 46% to 56% from 2009-2010) so both ethnic groups represent plausible drivers of future growth. Of course, access to the Internet is just half the battle: the real challenge is convincing Internet users who aren't members of social networks to convert, which may well require different recruiting strategies, varying by ethnicity, age, gender, income, educational background, etc., although it seems to me the basic selling points of online social networks are the same, regardless of cultural context.

Even if the total number of people using social networks stalls, individual social networks can still continue growing by persuading Americans to join multiple networks. Although it wouldn't grow the proportion of the U.S. population on social networks, getting users to double up would allow the networks to scale up and advertisers to reach consumers through more channels. This would simply require networks differentiating themselves in the minds of users, which should be easy enough if they actually have different purposes (e.g., Facebook vs. Twitter vs. LinkedIn).