Earlier this week I looked at the demographics of blog readers which showed that the younger the user, the more likely he or she was to read or keep a blog on a weekly basis.

I focus so much on demographic data because it is important to understand who is using social networking sites before you start advertising on them. Recently I looked at some new social network user demographics which indicated that the Facebook demographic skews female and under 25, compared to other major social networks. That is important information to know if you are building a Facebook application.

One of the fastest growing U.S. demographics are baby boomers, who have the discretionary income that advertisers love. But do baby boomers use social networks? Not according to a new study from JWT BOOM/ThirdAge “Boomers, Healthcare and Interactive Media” study conducted last month. They believe that less than one-quarter of US Internet users ages 40 and over use social networking Web sites.

The JWT BOOM/Third Age figures on social networking usage by those 40 and older generally agree with a study by ExactTarget conducted last month.

Instead of using one large category of older Internet users, ExactTarget divided users who were ages 35 and older into 10-year increments, with 65 and over being the oldest cohort. Although 39% of 35 to 44 year-olds used social networks, use fell sharply with age: Only 13% of 55 to 64 year-olds were social networkers, and only 4% of those ages 65 and older. In comparison, three-quarters of Internet users ages 15 to 24 use social networking sites.

Why don’t consumers 40 and older use MySpace and similar sites in greater numbers? Respondents said their main concerns were privacy, time and just not seeing the point. Although each of these barriers can be addressed, marketers might also consider that social networks are just not yet the best way to reach boomers.

It is always interesting to hear the objectives as to why people will not use something. As people age, I can understand why they would not find a site like MySpace or Facebook useful because it is aimed at a younger demographic. The opportunity I believe for marketers is through smaller niche social sites like cater directly to the boomers generation. For example the AARP has added a social networking section to its web site. This type of site would alleviate the boomers concerns with privacy and lack of information.

From a marketing perspective, advertisers who are looking to reach baby boomers would be better suited finding smaller niche sites like AARP rather than MySpace or Facebook.

I came across a fascinating report on the demographics of social network users. Rapleaf ooked at user profiles and demographcs for the major social networking sites (MySpace, LinkedIn, Friendster, Plaxo, and Hi5 ) as well as for Facebook. The data is fascinating.

Summary Numbers

• The greatest overlap between OpenSocial container sites exists between MySpace and Hi5, in which 43% of Hi5 users also use MySpace.
• Facebook users are 63% female and 36% male whereas the sites integrated with the OpenSocial platform are 61% female and 38% male
• 52% of Facebook users are 18-25, whereas 40% of the users are 18-25 for the five container sites on the OpenSocial platform
• Facebook users tend to use 2.9 major social networking sites on average whereas users of OpenSocial container sites tend to use 2.7 major social networking sites

Interesting that this data shows that Facebook demographic skews female and under 25, compared to other major social networks. That is important information to know if you are building a Facebook application.

Social Network Specific Data

Facebook Users

• 2.6 million users identified in Rapleaf
• 63% female, 36% male
• 17% <18 yrs, 52% 18-25 yrs, 21% 26-35 yrs, 5% 36-45 yrs, 5% >45 yrs
• 2.9 major social networking sites used on average
• 62% are on MySpace, 5% are on LinkedIn, 9% are on Friendster, 10% are on Plaxo, 22% are on Hi5

MySpace Users

• 11.3 million users identified in Rapleaf
• 63% female, 36% male
• 20% <18 yrs, 40% 18-25 yrs, 27% 26-35 yrs, 7% 36-45 yrs, 6% >45 yrs
• 2.4 major social networking sites used on average
• 15% are on Facebook, 2% are on LinkedIn, 9% are on Friendster, 6% are on Plaxo, 17% are on Hi5

LinkedIn Users

• 0.8 million users identified in Rapleaf
• 38% female, 61% male
• 2% <18 yrs, 9% 18-25 yrs, 49% 26-35 yrs, 24% 36-45 yrs, 16% >45 yrs
• 3.2 major social networking sites used on average
• 16% are on Facebook, 25% are on MySpace, 12% are on Friendster, 16% are on Plaxo, 8% are on Hi5

Friendster Users

• 2.3 million users identified in Rapleaf
• 58% female, 41% male
• 12% <18 yrs, 39% 18-25 yrs, 36% 26-35 yrs, 7% 36-45 yrs, 5% >45 yrs
• 3.0 major social networking sites used on average
• 10% are on Facebook, 44% are on MySpace, 5% are on LinkedIn, 5% are on Plaxo, 26% are on Hi5

Plaxo Users

• 1.3 million users identified in Rapleaf
• 62% female, 37% male
• 16% <18 yrs, 39% 18-25 yrs, 24% 26-35 yrs, 10% 36-45 yrs, 11% >45 yrs
• 3.6 major social networking sites used on average
• 20% are on Facebook, 53% are on MySpace, 11% are on LinkedIn, 9% are on Friendster, 15% are on Hi5

Hi5 Users

• 4.5 million users identified in Rapleaf
• 60% female, 39% male
• 21% <18 yrs, 44% 18-25 yrs, 23% 26-35 yrs, 6% 36-45 yrs, 6% >45 yrs
• 2.8 major social networking sites used on average
• 13% are on Facebook, 43% are on MySpace, 2% are on LinkedIn, 13% are on Friendster, 2% are on Plaxo

What I am amazed at is the number of people from the other social networks that use Hi5 (http://www.hi5.com). This is a social network that rarely gets any press, but for marketers it might be cheaper and easier to market on Hi5.com compared to Facebook or MySpace and still reach a lot of the same people.