Online advertising revenue was 11.5 billion dollars in the first half of 2008, an increase of 15.2 percent, according to a report by the Interactive Advertising Bureau and PricewaterhouseCoopers. Search advertising revenue show the largest increase of any format, an increase 23.6 percent to 5.1 billion dollars. Display advertising revenue, which includes display banner ads, rich media, digital video, and sponsorship, increased 18.8 percent to 3.2 billion dollars. Classifieds revenue decreased 5.2 percent to 1.6 billion dollars, referrals/lead generation revenue increased .8 percent to .8 billion dollars, and e-mail revenue increased 15 percent to .2 billion dollars. Performance based advertising accounted for 52 percent of revenue, with cost per thousand (CPM) accounting for 44 percent and hybrids accounting for 4 percent.