John Mueller of Google confirmed on Friday’s webmaster hangout video that Google does and can use historic or legacy data about your web site for ranking purposes. He gave a few examples of how Google uses it; your links over time, the adult SafeSearch filter and some of Google’s quality algorithms.
The question came up at 21:25 minute mark. Let’s jump to the quality algorithms part, where John said “similarly with some of the quality algorithms it can also take a bit of time to kind of adjust from one state to another state. So if you significantly improve your website then it’s not that from one crawl to the next crawl we will say oh this is a fantastic website now. It’s something we’re probably over the course of a year maybe sometimes even longer our algorithms have to learn that actually this is a much better website than we thought initially. And we can treat that a little bit better in the search results over time.”
So yes, if you do stuff where Google loses trust in your site and the quality algorithms are involved, it can take a year or more for Google to trust your site again.
Here is what John said in terms of how a site earns links over the years. “So in particular if you have a website that has existed for a very long period of time then that’s something where the whole ecosystem around the website will will have evolved around around that. Snd there’ll be links from all over the web for a longer period of time and when we look at that website we will see kind of the the current snapshot of the website what we recently crawled but all of these signals that have been collected over the years.”
Of course, the adult SafeSearch filter takes time as well.