ClickZ reports sponsored link impressions on Google and Yahoo! grew 16 percent in the past six months, according to data released by Nielsen//NetRatings .
That study shows that "sponsored link advertising impressions" grew from 55.4 billion to 64.3 billion over the past six months (August 2005 and January 2006).
Google in August 2005 earned 36.2 billion, which increased to 41.1 billion in January 2006, a six-month increase of 14%. Yahoo percentage growth was larger than Google’s, accounting for 19.2 billion in August of 2005 with an increase to 23.2 billion in January 2006 or a 21% increase in the past six-months. These figures include all of Google’s and Yahoo’s search partners and contextual networks.