Google has offered a general explanation of how it ranks its search results, one day after the European Commission said it was looking into antitrust complaints against the company.

In a blog post Thursday, Google Fellow Amit Singhal also referred to a recent op-ed piece suggesting that regulators should control how search engines rank results. He stressed that developing search rankings is very difficult, implying perhaps that regulating search would be hard for any government to do well.

Laying out the challenge, Singhal said Google processes hundreds of millions of queries a day, with at least 20% of them totally new. To handle the volume and variety of queries, the company uses a collection of algorithms to sift through data.

"Our algorithms use hundreds of different signals to pick the top results for any given query. Signals are indicators of relevance, and they include items as simple as the words on a webpage or more complex calculations such as the authoritativeness of other sites linking to any given page," he said.

On a typical day, Google makes one or two changes to the signals and its algorithms to try to improve results, he said.

The company doesn't manually choose any results, however, he said. "We believe that approach which relies heavily on an individual's tastes and preferences just doesn't produce the quality and relevant ranking that our algorithms do," he wrote.

To show there is room for improvement in its own rankings -- and perhaps to suggest that Google doesn't favor its own sites -- he noted that the query "search engine" does not list Google in the top few results.

There is nothing in the post that Google has not revealed before, but the company said news of the Commission's investigation had prompted "lots of questions" about how Google's ranking works.

On Wednesday, the Commission confirmed it was looking into three complaints against Google in the preliminary stages of an antitrust investigation. Google pointed to Microsoft as the source of the investigation, since Microsoft owns one of the companies that complained and is linked to another.

One of the complaints was filed by Foundem, a U.K. price comparison site. Foundem's co-founder wrote the op-ed piece that Singhal links to, which suggests that regulators should set rules for how search engines rank results. The editorial accuses Google of exploiting its dominance in search by displaying its own services at the top of search results, something that Google denies.

Source: ComputerWorld