Google continues to add social signals to its algorithm every day, and there are two driving indicators that influence how a website ranks: popularity and authority. But how do you separate these two?

“We’ve actually thought about this quite a bit because from the earliest days it would get us really kind of frustrated when we’d see reporters talk about PageRank and say PageRank is a measure of the popularity of websites because that’s not true,” Cutts said. “For example, if you’re to look at sites that are popular, for example porn sites are very popular, but people tend not to link to porn sites. On the other hand, if you take something like the Wisconsin real estate board, probably not a ton of people go there, but quite a few people do link to government websites.”

Certainly, this is true. If PageRank was based entirely upon popularity, which wouldn’t be a strange idea in itself, we would definitely see a different bunch of websites with a higher PageRank than they currently have.

“So popularity is some sense is a measure of where people go, whereas PageRank is much more a measure of reputation, it’s much more reputation of where people link, and there is a disparity there or else porn sites would have the highest PageRank and government sites would be very, very low within our ranking system, and that’s not the way that things work. We tend to see more links to reputable government websites.”

So Google can separate between popularity and authority, and in a very clever way we suspect. But based on these factors, how does it decide which search results to show for a specific query?

“Well it turns out you can say take PageRank for example, if you want to do a topical version of PageRank, you could look at the links to a page and say, ‘OK suppose it’s Matt Cutts, how many of my links actually talk about Matt Cutts?'” he said. “And if they are a lot of links or large fraction of links that I’m pretty topical, or maybe an authority on the phrase Matt Cutts.”

It seems then that the best tactic for SEO is to make your site, or even your persona a recognised authority within your particular market area. You’ll not only reap the benefits in the search ranking but you will also benefit from other members in your industry who are now perceiving you as an authoritative figure and will start promoting you and linking to you because of it.

“So it’s definitely the case that you can think about not only taking popularity and going to something like reputation, which is PageRank, but you can also imagine more topical or you’re an authority in the medical space, or you’re an authority in the travel space or something like that,” Cutts said. “By looking at extra signals where you can say oh you know what, as a percentage of the sort we see you are doing well for, or whatever, it turns out your links might be including more anchor text about travel or medical queries or something like that.”

Cutts also gives us some insight into some algorithmic changes that may be coming. Google will begin to separate more sites from simply being popular and sites being authoritative within their industry. He uses the example of medical queries, and this could point towards changes made on the algorithm that’ll be targeted to specific niche areas.

“So it is difficult, but it is a lot of fun. We actually have some algorithmic changes that try to figure out hey this site is the better match for something like a medical query,” Cutts said. “And I’m looking forward those rolling out because a lot of people have worked hard so that you don’t just say oh this is a well-known site therefore should match for this query, it’s this is a site that actually has some evidence that it should rank for something related to medical queries, and that’s something where we can improve the quality of the algorithms even more.”

Of course, Cutts doesn’t give us any indication of when the changes will come about , but webmasters should be armed and ready all the same.