While it can be tempting to view conversation on Twitter as a cross-section of public opinion, a new study from the Pew Research Center finds that the demographics of active users differ from that of the general US population. The study found that 10% of Twitter users generate the majority of tweets on the platform – and of that subgroup, 69% identify as Democrats.

Conservatives continue to complain that Silicon Valley companies and social media platforms are openly biased against them. While the Pew study does not refute or support this idea, it does show that Democrats are more likely to be prolific Twitter users.

For the study, Pew conducted a series of surveys asking Twitter users to share their handles so they could be validated as real people. Pew ultimately focused on 3,518 individual accounts in the US

The first finding is not entirely surprising: Power users dominate the platform. According to Pew, 10% of users produce 92% of all US tweets. Pew noted that the mean Twitter user in the US only posted one tweet per month. For Democrats, that average is one tweet per month, while for Republicans, it’s closer to zero.

Pew then took a deeper look at the political makeup of these power users.

The study found that 69% of people labeled “highly active users” identified themselves as democrats or democratically oriented independents. Within this most active subgroup, the researchers found that the 10% most active Democrats tweeted 157 times per month, compared to 79 times for the 10% most active Republicans.

“Most US adults rarely post on Twitter,” the study says. “But a small fraction of the highly active users, most of whom are Democrats, produce the vast majority of the tweets.”

Within the Democrats and Republicans categories, there was another important difference: Democrats on Twitter tend to lean a little further to the left than non-Twitter Democrats. According to Pew, 60% of Democrats refer to themselves as “liberal” on Twitter, compared to just 43% of Democrats who do not use Twitter.

In contrast, Republican Twitter users seem to be more in line with the generally conservative sentiment. According to the study, 60% of Republican Twitter users and 62% of Republicans who do not use Twitter consider themselves “very or slightly conservative”.