Google released data which seems to indicate that ad position does not affect conversion rates for single advertisements.
Google’s Chief Economist Hal Varian stated that many advertisers believe that since Google ranks ads by the bid x ad quality, those ads in higher positions tend to have higher quality which leads to higher conversion rates. Clearly a correlation between auction position and conversion rates but Varian argues that “the real question is how the conversion rate for the same ad would change if it were displayed in a different position.”
Varian and his team at Google have used a statistical model to account for this effect and found on average that there is very little variation in conversion rates by position for the same ad.
For example, for pages where 11 ads are shown the conversion rate varies by less than 5% across positions. In other words, an ad that had a 1.0% conversion rate in the best position, would have about a 0.95% conversion rate in the worst position, on average. Ads above the search results have a conversion rate within ±2% of right-hand side positions.
Have you seen better conversion rates from keywords you have a top position for, or is your conversion rate fairly steady for a single ad?