Hal Varian, writing on Google's Inside AdWords blog this week, confirmed that the higher up a pay-per-click ad appears, the more clicks it tends to receive. However, he said, Google research revealed that ad position has minuscule impact on actual conversion.
Varian and his team used a statistical model to indicate that conversion rates of paid ads vary by less than 5% across a sample of 11 ads. “An ad that had a 1% conversion rate in the best position would have about a 0.95% conversion rate in the worst position, on average. ... The bottom line: Conversion rates don't vary much by position,” Varian said.