I'm sure that everyone interested in SEO has wanted to know what kinds of percent increase in traffic is possible through natural search engine optimization techniques. We have an idea for a controlled study that would help gain insight into this, but before that's possible, we want to find out what else is out there.

Has anyone here seen any similar reputable studies that have already been conducted and released online? We've already found a ton of generic "case studies" illustrating the success of whatever SEO company published it, but few of those have specific numbers, descriptive data, percent changed, or any other truly useful data (because they are usually a barely disguised advertisement anyway).

I'm looking for a more reputable study about natural SEO and the potential for traffic increase.

Does anyone have suggestions? I'm sure this information would be useful to anyone else reading this as well.

Thanks in advance