Adverts within search results have “no measurable benefit” according to a paper published by eBay in conjunction with researchers from Berkeley and Chicago universities.

After giving their researchers the ability to experiment with how and when the company purchased search adverts, the company found that paid search results have very little effect on sales at all, and warned that “much of what is spent on internet advertising may be beyond the peak of its efficacy.”

Confirming what many have long suspected, the results of the study showed that when brands buy adverts based around common brand keywords, they are paying for clicks that customers would make anyway, with “almost all of the forgone click traffic and attributed sales…captured by natural search”.

When looking at more generic search terms without a particular brand name attached, the news was slightly better. Without a brand keyword, the placement of a given company in the results varied widely depending on the search terms, but research also showed that dropping down the search results had very little impact in terms of sales.

Working with eBay, the researchers stopped all non-branded advertising for 30 per cent of the US for 60 days, and found that doing so had a “very small and statistically insignificant effect on sales”. The report continued to say that “on average, US consumers do not shop more on eBay when they are exposed to paid search ads.”

One ray of hope for those spending money on search ads was the finding that recent or infrequent users were still impacted by paid results, with those who had been eBay users for less than a year, or who had completed only one or two transactions in the past year more likely to be impacted by the ads.

Still, the report may cause some concern for Google, who are the biggest seller of search adverts in the world. Of the $37bn (£22bn) the company made from its various websites in 2013 (two thirds of its gross revenue for the year) it is believed the majority of that income came from paid-for search results.