Regular readers of my blog must think I'm going at bit cuckoo of late, repeatedly quoting from a 20-year old book written by a guy born in 1911.

No apologies - David Ogilvy's book "Ogilvy on Advertising" is a classic. The man himself spent more time in the research department than on the creative team during his early years. He developed an heavier reliance on research and hard data than almost all his competitors:

Partly because it is so closely tied to marketing, the SEO business creates a lot of noise and opinions, with much "wisdom" being passed along from with opinion rather than data to back it up. After we published our SEO test results yesterday, we had people asking whether other similar studies had been published.

Well, there are surprisingly few real case studies available in the public domain and below is a link to three of the best. None of them employ complicated methodology or test more than a handful of sites, but they do at least provide some evidence to help you make your SEO decisions:

• How long does it take a new site to rank in the Search Engines? A useful post, showing that Google really does take longer to index and rank than Yahoo or MSN.
• Do outbound links help a page rank for a particular term? The result was a clear "no" and the author recommends that you only add outbound links to your less important pages.
• What is the best structure for a page title? Shows that Google prefers [Keyword Phrase - Site Name] whereas MSN prefers just [Keyword Phrase]. Yahoo's results were inconclusive.

Are there are any more useful case studies that we've missed?