If I were to ask you to name the top three social networking sites, you could probably answer easily. If I asked you to name the next five, you might find it a bit more difficult. You may be surprised to hear that Wikipedia has a list of nearly 200 active major social networking sites across the globe. Of these, I was interested in the top 20 social networking sites in the US when building the Forrester Research Social Media Forecast, 2013 To 2018 (US).

I had several research questions in mind. Which are the top 20 social networking sites in the US? How many unique monthly visitors do they attract? How much time do visitors spend on these websites? How many visitors access these websites via mobile? Which of these websites are most important for marketers? What is the share of social media spending within total online advertising spending? How much can it grow? What will drive growth? This last question was of particular interest to me. We believe that mobile will be a key driver for social media spending growth. Here’s why:

  1. More users are accessing social networking sites through mobile. As per our forecast, we expect the number of US social media users accessing social networking sites via mobile to exceed 200 million by 2018. Nearly one-fourth of them will be mobile-only social media users; the rest will access social networking sites via both PC and mobile.
  2. The share of time spent on mobile social networking apps continues to increase. Social media apps are among the top apps that smartphone users use. The amount of time they spend on these apps continues to increase.  
  3. Mobile ads provide a better return on investment (ROI) for marketers. Several studies have shown that the click-through rates (CTRs) for mobile ads on social networks is much higher than for desktop ads. Mobile ads provide a better ROI for marketers.
  4. Mobile ads earn more money for social media vendors than desktop ads. Studies have shown that native ads — ad units targeted according to social signals such as relationships, likes, and retweets — are more engaging than standard ads. Native ads are popular on mobile because of the limited screen size. The native ads on mobile earn more money for vendors than native or standard ads on desktops, either on a cost per click (CPC) or a cost per thousand impressions (CPM) basis.
  5. The overall mobile ad ecosystem will evolve. Mobile ads on social networks are much newer than online display or search ads. Online display ads have been around for nearly 20 years, while online search ads have been around for more than 10 years. While the online advertising ecosystem (comprising ad networks, ad exchanges, demand-side platforms, sell-side platforms, data management platforms, etc.) is somewhat mature for display and search, it will evolve for mobile social over the next five years. 

In our Forrester Research Social Media Forecast, 2013 To 2018 (US), we forecast that the US mobile ad spending on social networks will reach $4.5 billion by 2018. We expect the spending on mobile ads to grow nearly twice as fast as the spending on desktop ads on social networks. We believe that the future of social is mobile.