In the last three quarters, our data shows that website pages that update at least once per year gain an average of 4.6 positions in the SERPs versus pages that haven’t been updated.

… In the last three quarters, our data shows that website pages that update at least once per year gain an average of 4.6 positions in the SERPs versus pages that haven’t been updated. There is likely an even greater benefit to updating quarterly or monthly.