NEW YORK: The median age of social media users on top sites ranges between 30 and 44 new research has found, meaning marketers can no longer simply assume they're reaching a particular demographic when advertising there.

The findings come from GfK MRI's Survey of the American Consumer, which is derived from continuous surveys of approximately 25,000 US adults annually.

The youngest social site was Instagram where the median age was 30, the oldest LinkedIn at 44.

At the largest site, Facebook users are getting older: the median age of users has increased from 29 in 2009 to 40 today.

YouTube (38), Google+ (42) and Pinterest (38) also tend to have an older age profile while Twitter (32) more resembles Instagram.

In fact, millennials represent 70% of Instagram and 61% of Twitter users.

"These results clearly show that many of the social media applications are becoming mainstream, which bodes well for the long term viability of those companies," said Florian Kahlert, Managing Director of GfK MRI.

"At the same time, this growing acceptance raises the bar for media planners (and inventory sellers), because just adding social media sites to a plan without other sophisticated targeting no longer automatically increases your younger or savvy target groups."

Most sites display some degree of gender bias. Across the seven major social and photo/video sharing sites, men outnumber women among users in just three: LinkedIn (55% of users versus 45%), Twitter (54% to 46%) and YouTube (51% to 49%).

Women are the majority of users of Facebook (57% versus 43%), Google+ (53% to 47%), Instagram (60% to 40%) and, most notably, Pinterest (81% to 19%).

The study also showed that LinkedIn has the highest median household income (approximately $112,500) and the highest education levels among the top social sites.

And in terms of education, two-thirds (65%) of LinkedIn users fall into the "graduated college plus" category, compared to 29% of all adults. Pinterest users rank second in education level, with 41% registering as "graduated college plus".

Data sourced from GfK MRI; additional content by Warc staff