SEM Market Structure

In 2006, North American advertisers spent US$9.4 billion on search engine marketing, a 62% increase over the prior year and a 750% increase over the 2002 year. The largest SEM vendors are Google AdWords, Yahoo! Search Marketing and Microsoft adCenter. As of 2006, SEM was growing much faster than traditional advertising and even other channels of online marketing.

Nielsen Online, Mega View - Search Engine Query Shares 2008