Twitter usage doubled since late 2010, Pew study finds

The fraction of "online" adults who use Twitter on a typical day has quadrupled over the past 18 months -- to 8 percent from 2 percent, according to a new Pew report on Internet use. Eight percent is roughly one user in twelve (a little less, actually.)

Pew defines an online adult as someone who uses the Internet and/or e-mail, at least occasionally. According to Pew, 80 percent of all U.S. adults go online.

Smartphones may have had something to do with increased Twitter usage, Pew suggests, "because smartphone users are particularly likely to be using Twitter."

Pew found that one in five smartphone owners are Twitter users, with 13 percent using the service on a typical day. In contrast, about nine percent of Internet users who own more basic mobile phones are likely to use Twitter overall, and just three percent of basic phone owners use Twitter daily.

Daily usage has doubled since May 2011. Overall Twitter usage has also doubled since November 2010, but has leveled out considerably over the last year. As of February 2012, 15 percent of online adults reported using Twitter -- not a huge increase over the 13 percent Pew found in May 2011.

The report also broke down Twitter user demographics. Some tidbits in the report:

• African-American Internet users have taken to Twitter at a much higher rate than the general online population. More than one in four "online" African-Americans use Twitter, with 13 percent doing so on a typical day.
• About one quarter, or 26 percent, of internet users ages 18-29 use Twitter, nearly double the rate for those ages 30 to 49. Among the youngest internet users, ages 18 to 24, 31 percent are Twitter users.
• Residents of urban and suburban areas are more likely to tweet than their rural counterparts.

Update, 11:13 a.m. PT: Updated with more statistics from the report.