At this point, is there anyone on Twitter who is not a politician or a journalist? It turns out maybe not: Twitter has fewer users than LinkedIn and Pinterest, according to a Reuters survey released Tuesday. Pinterest’s enormous growth continued in 2013, with 21 percent of people surveyed saying they used the site, up from 15 percent in 2012. Twenty-two percent of those surveyed, meanwhile, used LinkedIn. Twitter trailed with just 18 percent of users, although it remained popular with the younger generation and blacks. Twitter also had a high level of user engagement. Facebook remained the dominant social network, with 71 percent of respondents saying they used Facebook and just 7 percent saying they don’t use their accounts. Reuters surveyed 1,445 Internet users ages 18 and older.