More than 66 percent of online adults in the U.S. belong to at least one social network. Facebook, as you probably imagine, is the 800-pound gorilla, with 845 million active users. Twitter has 127 million active users, Google+ has 90 million.

An infographic from OnlineMBA goes inside the demographics of these social networks and others, and explains the reasons Americans belong to social networks. Here are the top seven reasons (respondents were allowed to choose more than one, hence the percentages exceed 100 percent):

1. Stay in touch with friends (67 percent)
2. Stay in touch with family (64 percent)
3. Reconnect with old friends (50 percent)
4. Connect with people who share similar interests (14 percent)
5. Make new friends (9 percent)
6. Read comments from celebrities, athletes or politicians (5 percent)
7. Find potential romantic partners (3 percent)

Here’s the full infographic: