Platforms such as Google and Bing offer companies the option to "buy" words. This means their websites appear more prominently if a person searches for a particular term.
The eBay study found that most people who clicked through as a result of this service were loyal customers who would have come to the site anyway.
"Incremental revenue from paid search was far smaller than expected because existing customers would have come to eBay regardless, whether directly or through other marketing channels," said an eBay representative.
In carrying out the study, presented at an economics conference held at Stanford University, eBay removed its paid-search keywords from MSN and Yahoo platforms in the US, while retaining them on Google.
They found that without the advertising, users still clicked through as the results appeared on the search engine anyway.
Source: BBC News
