Over the years it has been a challenge to stay on top of the changing relationships in the world of search.  To keep up with the latest, we have always referenced the Search Engine Relationship Chart created by Bruce Clay.  The chart is a visual depiction of the connections between search engines, organic listings, and advertising networks. 

On a recent visit to Bruce Clay's website, we came across something even more interesting, a histogram showing search engine relationships over the past seven years.  You can visually trace the history of search marketing back through the years, and watch Google's rise to prominence in paid search.

Pretty cool.  Thanks to the folks at Bruce Clay, Inc for putting this together.