A study by the shows that the average CPC shot up from 6p to 29p on brand terms between January 2008 and March 2009, while click-through rates declined from around 40 per cent to 20 per cent during the same period.
The data submitted by 12 agencies on behalf of 47 brands raises questions over the efficiency of paid search on brand terms at a time when marketers are looking to maximise ROI.
Google introduced a number of fundamental changes to its AdWords platform during the period in question, most significantly relaxing its PPC policy to allow brands to bid on keywords trademarked by rivals.
The search giant claims it introduced the changes to improve the consumer experience, but it faces ongoing accusations of knowingly driving up the cost of search to boost revenue during the recession.
"The declining click-through rate challenges the notion that Google's trademark change was in order to benefit the users," says Arjo Ghosh, chair of the IPA Search Council and chief executive of iCrossing. "To understand the full picture it would be good to see an analysis of user behaviour in paid and natural search."
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