In August 2006 AOL leaked some data to the public, and within this data contains the click through rates from the search engine listings. As you can see below the #1 result for any given query gets approximately 47% of the click throughs, where as #2 gets 34% less traffic.

#1 – 47% click-through
#2 – 13% click-through
#3 – 9%click-through
#4 – 7% click-through

Being number 1 for all your keywords that bring your revenue is very important, make sure your on top of your SEO!