Traffic to the largest classified advertising websites has grown by almost 50% in the last year, according to new research.

Research group comScore says 37.4 million US users visited the top consumer-to-consumer ad sites in July, a rise of 47% over the same month in 2005. was the most popular, doubling its unique visitors to almost 14 million during the month. Trader Publishing, the leader in July 2005, ranked second with 10.2 million visitors (up 15%), while AutoTrader ranked third with 6.4 million visitors (up 14%).

While online classifieds are not new, it appears that internet users are really beginning to catch on to this phenomenon,” said Andrew Lipsman, senior analyst at comScore.

With nearly fifty percent growth in the past year, online classifieds are growing at a rate that surpasses most other categories. As the category leader, Craigslist has clearly impacted the way in which new and traditional media companies approach the classifieds business.

ComScore said a higher than expected proportion of visitors came from among younger professionals. People between the ages of 25 and 34, and those in households making at least US$100,000 annually, were each 23% more likely than average to visit classified sites.