Thoughts on CTR on both PPC and SERPS

I've been trying to get my head around what kind of CTR I can expect to my website for both the PPC advertising that I use and from my natural position on Google Search Engine Results Page.

I would really appreciate the thoughts of anyone on this forum with a better understanding of this than I.

I found some metarial on the web that gave the following click through rate based on SERPS position. It is based upon a total of 20,000 serches for a specific keyword and I have rounded the figures up or down.

Position Clicks

1 42%
2 12%
3 8%
4 6%
5 5%
6 4%
7 3%
8 3%
9 3%
10 3%
11 0.66%

For a particular keyword (Space Toys) I believe that there are 400 searches per day (Australia) and I am currently getting about 15 hits per day for this keyword. This amounts to a CTR of 3.5% which seems to agree with the above table since I am ranked Google number 7 for this particular keyword.

Does anyone else have any information on CTR based on SERPS which either agrees or disagrees with the above table ? It seems that there is a huge difference between just being on the first page and being in the top 3 in Google.

I'll be working on my site to try and improve this number 7 position for this particular keyword but in the meantime I'm also using adwords to try and get better exposure. So I pay my nominal amount and get position 1 or 2 for the term "Space Toys" within adwords.

From that number 1 or 2 position I get about 10 clicks per day (2%) for the same term and based upon about 400 impressions. I know that "Space Toys" is a fairly general term so it's not going to have a high CTR but it still seems pretty low compared to the number 1 position with SERPS on Google.

If the information that I have found is correct then if I were number 1 in SERPS on Google then I could expect 160+ clicks from 400 searches for the aforementioned term. Yet, when I'm number 1 in adwords for PPC I can expect only 10 clicks for the same term.

It seems odd that while 42% of users will click your site if it is ranked number 1 in google for the term that they searched and only 2% of users will click your same site with the same message if it is a PPC advert at the top or right hand side of the page.

Are my calculations correct or is the information on SERPS and CTR that I have found, out of date or wrong ? Does any one else have any thoughts on this ?

Cheers

Martin