Forrester Research, an international technology and market research company, has been formally tracking the growth and maturation of social media behavior over the past four years. Each year it has seen steady increase in participation – until now.

In its most recent study, just released, Forrester reports that although social media “joiners” and “spectators” continue to grow in the U.S., the number of “creators” has now reached a plateau.

Forrester defines social media “creators” as those people who maintain a blog, publish their own web pages, or upload their own videos or musical creations. As of today, Forrester estimates that approximately 23% of U.S. online adults fall into this category.

But for the first time since Forrester’s annual “Global Social Technographics®” studies began in 2007, the number of “creators” hasn’t risen. In explaining this news, Augie Ray, senior analyst of social computing/marketing at Forrester, had this to say in a 9/28/2010 blog post:

“The reasons span things as complex as human nature and as simple as web site usability. For example, is it sensible to believe that ‘creator’ behavior will ever be universal? Not every person has a burning need to be a reporter, an industry expert, a videographer, a musician, a thought leader, an editor or a broadcaster. The fact that more than one in five online adults in the U.S. are exhibiting ‘creator’ behavior is a testament to how social technologies have lowered the bar, since these tools have allowed more people to create and distribute their ideas, opinions and creations than was ever possible in the past.”

The 2010 Forrester study did find that the number of “joiners” – those people who maintain social networking profiles – continues to grow. That’s explained by the fact that people feel they must be part of social media, if only to keep in touch with friends and relatives. Notes Ray, “Today, avoiding social networks is about as easy to do as avoiding e-mail – it’s possible, but it comes at a substantial cost in terms of relationships and knowledge.”

Another interesting aspect of the Forrester report is a look at the Social Technographics® ladder that does a nice job of breaking down social medial activities into behavioral categories. As of today, the research finds the following breakdown:

 ~23% are “creators” – They publish a blog or their own web page, or upload their own videos or music at least once per month.

 ~68% are “spectators” – They read blogs, listen to podcasts, watch videos, read online forums or read customer reviews at least once per month, without otherwise interacting with the content.

And what about the “inactives” – those who engage in none of the activities as described above? They represent just 19% of all American adults who are online. Based on the most recent findings, that’s a figure that may stubbornly refuse to decline much further.