Over the past four years, the use of online classified ads by U.S. adults has doubled, according to a study from the Pew Internet and American Life Project. Specifically, 49 percent of adult internet users say they’ve accessed an online classified, compared to 22 percent who did so four years ago. And on an average day, 9 percent of web users go to an online classified, up from 4 percent in 2005.

Anyone who’s looked at newspaper company earnings reports over the last year knows that that column is usually filled with double-digit declines. Since peaking at 19.6 million in 2000, Pew notes that newspaper classifieds have plunged nearly 50 percent to $9.9 million. Or since dropping to $17.3 million in 2005, newspaper classifieds have fallen another roughly 42 percent.

When talking about online classifieds, one site usually comes to mind: Craigslist, which had 42.2 million unique visitors in March. (Total unique visits to online classifieds numbered 53.8 million, a rise of 7 percent.) Despite its recent troubles over erotic ads, Craigslist is poised to continue its dominance of classifieds, as newspapers struggle to catch up.
(See the charts after the jump)