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Hello Claire, From what I have observed Google seems to give a boost to fresh content, or even re-freshed content. I have seen this effect in the following situations: When updating the publish date on the page- When updating the last-mod date in the sitemap When refreshing a page WITHOUT updating the publish date (though I don't know if the dateModified tag was updated.) As for empirical data, none that anyone is willing to share publicly. But this is a real effect that has been seen over and over again by myself, and several people I trust. Take it for what it's worth, but going back through old content and looking for ways to improve it, bring it up-to-date, and ensuring the last-mod tag in the sitemap gets updated is a very good use of your time as a marketer.