MOUNTAIN VIEW: Google has rolled out a modified search algorithm across its English-language services, in a bid to downgrade the rankings of low-quality content.

The algorithm was first released in the US just over a month ago. According to the search firm, the change affects the ranking of 2% of US sites.

Writing on Google's Webmaster Central Blog, Google Fellow Amit Singhal said: "We've gotten a lot of positive responses about the change: searchers are finding better results, and many great publishers are getting more traffic.

"We've found the algorithm is very accurate at detecting site quality."

Commenting on the move, digital marketing specialist Econsultancy said: "Google's drive to boost the quality of its index is of course a very good thing in principle, and publishers focused on providing high-quality content will hope that the changes reward them for their efforts.

"At the same time, however, one has to wonder if the speed at which Google is changing its algorithms and its desire to publicize those changes is motivated more by a genuine desire to improve the SERPs, or by a genuine desire to create the appearance that it is."

The precise nature of the algorithmic change has not been revealed by Google, though Singhal pointed out that in "high-confidence situations", sites blocked by users are beginning to be incorporated into the data.

Google recommended that publishers whose search rankings are affected by the changes contact the company.

"While we aren't making any manual exceptions, we will consider this feedback as we continue to refine our algorithms," Singhal added.

The algorithm change represents one of a series of innovations by search engines over recent months as they attempt to improve their services to users.

For example, Bing, a Microsoft-owned site, has begun to incorporate social media content by including "likes" registered by users' Facebook friends in its results pages.

Data sourced from Google/Econsultancy/Warc/comScore; additional content by Warc staff