In a year-long study, Pew found that the reaction on Twitter to major political events and policy decisions often differs a great deal from public opinion as measured by surveys – with overall negativity at odds with national findings.

More tweeters reacted favourably to President Obama’s re-election, first presidential debate and the California same-sex marriage ruling while conversely, Twitter reaction was more negative on Obama’s second inaugural speech, John Kerry’s nomination and the State of the Union address.

The issue stems from the narrow sliver of the public that are represented on Twitter, as well as who among that slice chose to take part in any one conversation.

Pew said that those who get news on Twitter are in a different demographic than the public with only 13% of adults saying they ever use Twitter, dropping to 3% that tweet or retweet news.

In addition, half of adults were younger than 30 and 46% who posted news on Twitter said they were Democrats.

Twitter also features users who are under 18 and who live outside the US – neither of which are included in surveys of American public opinion.

The report concludes: “Overall, the reaction to political events on Twitter reflects a combination of the unique profile of active Twitter users and the extent to which events engage different communities and draw the comments of active users.

“While this provides an interesting look into how communities of interest respond to different circumstances, it does not reliably correlate with the overall reaction of adults nationwide.”