Yes, there is! A 2006 study from Cornell University studaied the distribution of clicks on a SERP. How many more clicks does a #2 spot get over a #3 spot, etc.? They used eye-tracking to conduct the experiments, as well as a sample of undergraduate students performing 397 queries on various topics like music, movies, travel, local, politics, and trivia. Here are those results:
The results are staggering. But this organic SEO consultant already knew that the difference between #1 and #2 was gigagntic. I had a client that commanded the #1 spot for his main keyword for a very long time. Well he dropped to #2 and called me up freaking out, he said that he had lost about 40% of his business! Of course I got him back up there right away and he has been back at #1 since. I have many other stories from clients of just how much their business is affected. This study just solidifies, scientifically, what I have been preaching to clients all along. You can view the full story from SEO Researcher.
There are some valuable lessons to learn from this research and its results. When running an SEO campaign it is important to have focus. If the site you are working on has some existing rankings on pages1, 2, or even 3 and some of those terms carry some trafic with them then you need to work hard to get those terms to the top 3. Those terms are just on the cusp of seeing huge traffic gains. And it is much more reasonable to expect to move those terms to page 1 from 2 or 3 than it is to rank a term that the site is not even in the top 100 for. Focus on the terms that will bring good traffic that you can rank in the sortest amount of time. Then, once you have proven your self and provided the client with some gains and ROI, you can start to focus on the other terms.