UMass Dartmouth’s Center for Marketing Research has released its annual study of social media marketing, showing that a whopping 91 percent of firms use at least one social media tool. This is up from 57 percent two years ago.

One caveat here: This is among the “INC. 500” fastest growing private companies in the U.S. Though the figures show sharp growth, the sample would tend to include more technically savvy companies and thus skew results in favor of higher adoption. There’s nothing wrong with this — the figures are directionally relevant — but it shouldn’t be seen as representative of the overall market. 

Consider the small businesses, for example: They’re known to be at the lower end of the technology adoption scale — not to mention their lack of dedicated digital marketing resources. In our small-business marketing survey (LCM Wave 13), 32 percent of respondents report intention to use social media marketing in the next year but only 9 percent reported they currently use Twitter.

This will be a key topic discussed in a panel about social media and local marketing on Day 1 of next week’s Interactive Local Media conference. In the meantime, here are some other data points from the UMass study, as reported by eMarketer.