Pew: US adult Twitter users tend to be younger, more Democratic; 10% create 80% of tweets

It also notes that the activity on Twitter is dominated by a small percentage -- most users rarely tweet, while the most prolific 10 percent are responsible for 80 percent of tweets from U.S. adults. Pew says only around 22 percent of American adults today use Twitter, and they are representative of the broader population in some ways, but not in others. For starters, Twitter's U.S. adult users tend to be younger.