Phone? What phone? I'll Facebook you or send you a tweet, thank you very much. That's the sentiment of an increasing number of people these days, especially those under 30. According to a poll released by Pew Research Center in August 2013, 72 percent of online users use social networks. That's a huge increase from only 8 percent back in 2005. This represents a drastic and rapid change in the way we connect with one another. Even so, it's clear than not everyone is using social media, nor will you find your group of friends and connections on every social network. So who exactly is using major social networks? Here we take a look at user demographics for some of the top sites.

Tumblr: Hip Millennial Hangout

While it has shown robust growth, the blog that captured the tech world’s attention when it was acquired by Yahoo for $1 billion in August 2013 is still very young, and its user base reflects that. Currently, only 6 percent of Internet users report using Tumblr. What is interesting about Tumblr is not so much how many people use it, but exactly who uses it. Tumblr's core user base is mostly made up of Millennials and Gen Xers who have recently entered the workforce. According to Quantcast, more than half of Tumblr’s users are under the age of 35. In addition, perhaps because Tumblr is such a visual platform, women out number men 52 to 48 percent. The largest share of Tumblr’s users are between the ages of 18 and 34, have no children and make under $50,000 per year. More than half of Tumblr’s users have either graduated or are attending college.

Twitter: The Every (Young) Person's Network

According to statistics released by GlobalWebIndex at the end of 2012, the number of global Twitter users is approaching 500 million. That's up nearly 100 million from just six months ago. In other words, Twitter is growing fast. While it has been used as a way for celebrities to express themselves (often to their detriment), millions of others use it as well. According to Pew Research, 18 percent of all Internet users were using Twitter, as of August 2013. Like Tumblr, a great deal of Twitter’s users are between the ages of 18 and 29. What we also know is that Twitter users tend to be from urban areas and its user base is one of the most ethnically diverse of all social networks. Twitter also has the most income diversity among its users - after Facebook. (Want to succeed on Twitter? Read Twitter Fail! 15 Things You Should Never Do On Twitter.)

Facebook: The Network Everyone Loves (to Hate)

Next up, Facebook - the mother of all social networks. What began as a social network for and by college students has become a widely used social phenomenon. According to Pew Research, 67 percent of Internet users are on Facebook, a number that's a great deal higher than any other social network. Facebook still maintains a very strong base of users who are either in college or have recently graduated college. As of August 2013, 73 percent of college students and 68 percent of college graduates reported having a Facebook account. What's perhaps most striking about Facebook, however, is the wide range of ages who have jumped on the network - like your mom. In fact, 73 percent of adults from the ages of 30-49 and a whopping 86 percent of adults from 18-29 use Facebook. While Facebook has attracted individuals of every income bracket, its user base includes a slightly higher share of those that earn $50,000 and up. (Needs some tips on navigating Facebook safely? Check out 7 Signs of a Facebook Scam.)

Pinterest: Most Pinteresting to Women

Pinterest is rapidly emerging as a major player in the social media industry and has experienced a tremendous amount of growth in just a few short years. According to Pew Research, 15 percent of Internet users are on Pinterest - almost all women. Only 5 percent of male Internet users log on, compared to 25 percent of women. Of course, that makes more sense when you've actually seen Pinterest, which is styled much like a typical women's magazine, except that it gives women am unprecedented platform to share visual content. What is especially interesting is the demographic of women that are attracted to Pinterest. A higher concentration of Pinterest’s users have gone to college and make more than $50,000 per year. While Pinterest’s user base hails from the suburbs and urban areas, a higher percentage are rural Internet users. For the most part, these users tend to be between the ages of 18-29; however, 12 percent of Internet users between the ages of 50-64 also use the service. Pinterest users tend to spend more, especially with retailers who have succeeded at visually leveraging their products and services. (For more insight, read Pinterest for Business: Why It's Harder Than It Looks.)

As more people use social media and make it part of their daily communications, we're likely to see even more obvious splits in the types of users on each network. But then again, in the social networking world, we all have a tendency to lose interest and move on to something else. Remember MySpace?