If you are suffering from Panda issues, or suspected ranking issues related to low quality content, the most obvious fix is to improve content quality.  But after you make major site-wide changes to improve the quality of that content, how long does it take for Google to adjust their ranking signals accordingly for the new and improved content?  And for a site-wide demotion effect, how long would it take to see improvement?

When it comes to improving an entire site, obviously rankings aren’t going to jump up the day after pushing the improved content live.  Googlebot still needs to crawl all the updated pages and then adjust their ranking signals accordingly.  So while you could see individual pages improve rather quickly, overall, it takes Google longer to crawl some pages than others.

The question came up in the last Google Webmaster Office Hours with John Mueller:

I don’ t think there’s any fixed time that we would have for something like this.    In general we try to recognize the quality of the content overall and recognizing bigger changes in the quality of your content means we have to reprocess everything first.  Which means some pieces of content will be reprocessed fairly quickly and others take quite a bit of time.

This is something I wouldn’t expect you to upload a copy of the website now and then tomorrow everything will be updated and rank completely differently. This is something that is a longer period of time – a longer term thing that will probably take several months for everything to be reprocessed and everything to be re-understood.  And sometimes that can take even longer.

So that’s something where there’s no fixed time frame, no stop watch you can set and say I uploaded my new version of my site and this time it’s actually good. That’s something that takes a bit of time and our algorithms really have to understand how things have changed.

So improving content is always a great thing to do for a site, but don’t expect it to be a quick fix where rankings will increase overnight.  It seems more of a long term game plan for improving rankings.  And you could see pages that Google already crawls more frequently see improvements faster than ones that Googlebot rarely visits.