10 statistics that demonstrate the value of SEO

These statistics source from a compilation of SERPS behaviour studies for which I’ve listed source information at the end of the article. If you disagree with a figure, or have additional figures or sources, please do post them to the discussion.

42% of search users click the top-ranking link. 8% click the second-ranking link, and the click-through rate (CTR) continues to drop thereof.
When these two top-ranking links are artificially switched, the click-through ratio of 42-8% drops to 34-12%, demonstrating the importance of engaging copy in addition to rank position.
62% of search users click a link on the first page of search results
23% of searches progress to the second page. Presumably the difference between 62% ans 23% stems from searchers trying either another keyword or another engine, or giving up.
80% f unsuccessful searches are followed with keyword refinement.
41% of searches unsuccessful after the first page choose to refine thir keyword search phrase or their chosen search engine.
77% of search users choose organic over paid listing when searching, 67% choose organic search when purchasing.
When the searcher is purchasing, organic click-through generates 25% higher conversion rates than equivalent Pay-Per-Click (PP) click-through.
40% of SEO campaigns aware of their ROI achieve returns in excess of 500%, while only 22% of PPC campaigns were able to achieve this value.
Daily use of search engines rose from 33% in 2002 to 59% in 2005. The average day in 2005 reported 60 million people using a search engine. As of March 2007, Google accounts for 64% of US searches and 77% of UK searches

The validity of these statistics depend on various experimental factors (i.e. large, representative samples of searchers/searches), and on accurate statistical analysis.

For more in depth analysis, the sources for this article were:

Please post addition figures or sources, or your view, in the comments.