Google updates their search algorithm every day
Google Search consists of several hundred ‘signals’ in their search algorithm and in a new video from Google, they say they change and update it every day, sometimes almost twice over. That is a tremendous amount of work that goes into providing the best search results possible.
In 2010, Google ran over 20K different experiments in their sandbox (test environment) to get better results. If the better results are approved, they go through an analysis stage so it can be approved and pushed to the live Google Search site.