Search giant Google has adjusted its famously secretive algorithms to push so-called “content farms” further down the lists of results that users see.

“This update is designed to reduce rankings for low-quality sites - sites which are low-value add for users, copy content from other websites or sites that are just not very useful,” said Google fellow Amit Singhal in a blog posted on Thursday night.

“At the same time, it will provide better rankings for high- quality sites - sites with original content and information such as research, in-depth reports, thoughtful analysis and so on.” Analysts said the move would likely have the greatest impact on companies like Demand Media, Associated Content and Suite 101, which generally produce content that is gleaned from other sites and which is primarily designed to appear high on frequently searched-for terms. News of the changes sent shares of Demand Media tumbling early on Friday, but the company said the move had not adversely affected its status.

“As might be expected, a content library as diverse as ours saw some content go up and some go down in Google search result,” executive vice president of media and operations Larry Fitzgibbons said in a blog post.

“It’s impossible to speculate how these or any changes made by Google impact any online business in the long term - but at this point in time, we haven’t seen a material net impact on our Content & Media business.” Singhal said the change noticeably impacts some 12 per cent of Google searches and would be introduced initially in the U.S. before rolling out internationally.