How is Google Chrome able to guess which folder to place a bookmark?

Usually the default folder offered is the last folder that was used to store a bookmark, but every so often Chrome takes a guess as to which folder to use and it does surprisingly well. I just came across the site Less Wrong. I have not spent any time on it, so I don’t know that much about it. I decided to bookmark it for future investigation. I was not sure where I wanted to place the bookmark, but Chrome offered my Advocacy folder, which seemed as good a spot as any. How did they come up with that?