Half as many US internet users click on ads as did 2 years ago

"The collaborative studies focus on an understanding of how U.S. Internet users click on display ads. The updated results based on March 2009 comScore data, and presented by comScore chairman Gian Fulgoni and Kim McCarthy, manager, Research & Analytics at Starcom, at the iMedia Brand Summit in San Diego on September 14, 2009, indicated that the number of people who click on display ads in a month has fallen from 32 percent of Internet users in July 2007 to only 16 percent in March 2009, with an even smaller core of people (representing 8 percent of the Internet user base) accounting for the vast majority (85 percent) of all clicks.
[...]
The original research, conducted using July 2007 comScore data, showed that 32 percent of Internet users clicked on at least one display ad during the month. These clickers were segmented into Heavy, Moderate and Light Clicking segments based on the group of users accounting for the top 50 percent of clicks (heavy), middle 30 percent (moderate), and bottom 20 percent (light). In 2007, comScore, Starcom and Tacoda found that heavy clickers represented 6 percent of U.S. Internet users, moderate clickers accounted for 10 percent and light clickers accounted for 16 percent. By March 2009, those numbers had dropped substantially in each case, to 4 percent of Internet users for heavy clickers, 4 percent for moderate clickers and 8 percent for light clickers."
Source: Natural Born Clickers report by comScore, Starcom USA and Tacoda, reported in a press release, 1st October 2009