A noted Google-watcher has assembled a convincing argument that the site's search results highly favor Google-owned services, despite repeated company claims that they are algorithmically generated and never manipulated.

Harvard professor Ben Edelman and colleague Benjamin Lockwood found that Google's algorithm links to Gmail, YouTube, and other house brands three times more often than other search engines. Search terms such as “mail”, “email”, “maps”, or “video” all yield top results featuring Google's services, they found. The practice, which Yahoo! was also found to engage in – albeit less blatantly – puts the search engines' interests ahead of users' need for unbiased data about the most useful sites on the web, they warned.

“Google asks the public to believe that algorithms rule, and that no bias results from its partnerships, growth aspirations, or related services,” they wrote in a report posted on Wednesday. “We are skeptical.”

What's more, they found that Google favored its own portal services even when click-through patterns made it clear that users preferred competing sites. Take searches for “mail”, for instance. Google's first result is for Gmail, even though a paltry 29 percent of users actually click on the link. By contrast, the second result, for Yahoo! Mail, was clicked on by 54 percent of users.

Not to be outdone, Yahoo! returned its own video.yahoo.com site as the top result for the search term "video", even though only 21 percent of visitors clicked through. YouTube was the second result and was followed by 39 percent of users.

By comparison, Bing showed remarkable restraint in shilling its own services. Searches for “mail” and “email” on the Microsoft-owned search engine didn't mention its Hotmail site in the top three results even though it's far and away the most widely used free web-based email service as measured by registered users.

The report comes as the European Union's Competition Commission is directing a set of hard-hitting and wide-ranging confidential questions to Google rivals, customers, and clients as it probes the world's number-one search engine for evidence that it abused its dominant position in paid search advertising. Google has denied those claims.

Google has long talked up the savviness of its algorithms in pointing users to the most useful pages on the internet. But Edelman and Lockwood dug up this YouTube clip from 2007 in which Google VP Marissa Mayer admits the search engine regularly favors its own brands.

When the company launched Google Finance, “We did put the Google link first,” she said in the hour-long clip, which far exceeds the 15 minutes most YouTube users are allotted for a single video. “It seems only fair, right? We do all the work for the search page and all these other things, so we do put it first. ... That has actually been our policy, since then, because of Finance. So for Google Maps, again, it's the first link, and so on and so forth. And after that, it's ranked usually by popularity.”

Edelman and Lockwood draw comparisons to arguments made in the 1990s that Microsoft used its dominant Windows market share to illegally promote Office and other fledgling apps. Most Reg readers will remember how the resulting antitrust probe ended.

“In the long run, just as Windows source code and APIs are subject to outside scrutiny, we expect that search algorithms will require similar external review,” they wrote. “Last month, the European Commission announced an investigation of biased results at Google, including 'alleged preferential placement of Google's own services.' We credit that effort, and our analysis suggests that the EC's investigation will indeed reveal that Google has intentionally put its own links first.” ®

Update

A Google spokesman emailed us the following response:

"Mr. Edelman is a longtime paid consultant for Microsoft, so it’s no surprise that he would construct a highly biased test that his sponsor would pass and that Google would fail. Google never artificially favors our own services in our organic web search results, and we perform extensive user testing to ensure that search results are ranked in a way that provides users with the most useful answer."