Facebook is driving an increasing amount of traffic to news sites but Google remains the top referring service according to a study published on Monday. The study by the Pew Research Center\'s Project for Excellence in Journalism looked at the behaviour of news consumers online during the first nine months of 2010 using audience statistics from the Nielsen Co. The study examined the 25 most popular news websites in the United States looking at how users get to the sites how long they stay there how deep they explore a site and where they go when they leave. An average of 40 percent of the traffic to the top 25 news sites comes from outside referrals the study found with Google Search and, to a lesser extent Google News the single biggest traffic driver. The Nielsen figures did not break down where the remaining 60 percent of a news site\'s traffic comes from but the study said much of it stems from direct visits to the home page of a news site. \"Far from obsolete home pages are usually the most popular page for most of the top news sites\" the study said and were the most viewed part of the site for 21 of the 25 studied. Google Search was responsible for driving an average of 30 percent of traffic to top news sites with the Drudge Report and Yahoo! also ranking as major traffic drivers. But social media and Facebook in particular is \"rapidly becoming a competing driver of traffic\" the study said. At five of the top 25 sites Facebook was the second or third most important driver of traffic. \"If searching for news was the most important development of the last decade sharing news may be among the most important of the next\" the study\'s authors said. The website drawing the most traffic from Facebook links was The Huffington Post with eight percent of its visitors landing on the site that way. Twitter somewhat surprisingly \"barely registers as a referring source\" the study found. Only one website in the top 25 the Los Angeles Times with 3.53 percent derived more than one percent of its total traffic from Twitter. Many visitors to top news sites are what the study described as \"casual users\" people who visit just a few times a month and spend a total of just a few minutes there at a time. On average 77 percent of the traffic to the top 25 news sites came from users who visited just one or two times the study said, with the percentage varying among sites. Yahoo! News had lowest number of people visiting only once or twice but it was still more than half at 55 percent. More loyal and frequent visitors what the study called \"power users\" return more than 10 times per month to a particular site and spend over an hour there over that time. But \"power users\" make up an average of just seven percent of total users among the top 25 sites, the study said. CNN had the most \"power users\" 18 percent while 16 percent of Fox New\'s audience fell into that category. Only six sites had \"power user\" figures in double digits. \"Overall the findings suggest that there is not one group of news consumers online but several each of which behaves differently\" the study said. \"These differences call for news organizations to develop separate strategies to serve and make money from each audience. \"Advertising may help monetize some groups, while subscriptions will work for others.\" As for where readers go when they leave a site Google is a leading destination accounting for up to seven percent of departure links. The study also noted the divide between Google and Facebook in that Google does not send users to Facebook and vice versa. \"Google and Facebook are increasingly set up as competitors sorting through the material on the Web\" it said. \"They are two fundamentally different ways to navigate the Web.\" The top 25 sites included 11 newspapers The New York Times The Washington Post USA Today The Wall Street Journal The Los Angeles Times the New York Daily News the New York Post the Boston Globe the San Francisco Chronicle the Chicago Tribune and Britain\'s Daily Mail. Six were the websites of broadcast or cable television networks MSNBC CNN ABC Fox CBS and the BBC and four were pure news aggregators Google News, the Examiner Topix and Bing News. Three were \"hybrid\" sites which mix aggregation of other news sources with original reporting Yahoo! News AOL and The Huffington Post and one was a wire service Reuters.