Put simply, sites that rank highly have higher Click Through Rates (CTR) and as a result, receive more visits. The graph above shows how the CTR drops off significantly after the #1 ranked site. The Google heat map below shows the same.
Many people like to use rankings as a way to measure the effectiveness of natural SEO efforts. Ranking reports are easy to pull and share. Using ranking reports to measure SEO effectiveness is flawed for the following reasons:
In your Analytics reports, check your organic search traffic. Filter your traffic in three ways:
An increase in branded search traffic is not a good measure of the effectiveness of natural search because the people who type branded phrases into a search engine are already familiar with your company. Natural search should reach potential customers that have never heard of your company. This is why measuring traffic on non-branded keyword phrases is the best measure of the effectiveness of natural SEO. It will measure the number of visits received from all keyword phrases, not just the few that you may have checked in a ranking report including many long tail keyword phrases you may not have considered.