Sponsored search accounts for 40% of the total online advertising market. These ads
appear as ordered lists along with the regular search results in search engine results
pages. The conventional wisdom in the industry is that the top position is the most
desirable position for advertisers. This has led to intense competition among advertisers
to secure the top positions in the results pages.
We evaluate the impact of ad placement on revenues and profits generated from
sponsored search using data for several hundred keywords from the ad campaign of an
online retailer. Using a hierarchical Bayesian model, we measure the impact of ad
placement on both click-through rate and conversion rate for these keywords. We find
that while click through rate decreases with position, conversion rate first increases and
then decreases with position for longer keywords. The net effect is that, contrary to
conventional wisdom, the topmost position in sponsored search advertisements is not
necessarily the revenue- or profit-maximizing position. Our results inform the advertising
strategies of firms participating in sponsored search auctions and provide insight into
consumer behavior in these environments.
Specifically, they help correct a significant
misunderstanding among advertisers regarding the value of the top position. Further, they
reveal potential inefficiencies in present auction mechanisms used by the search engines.