Does PR Flow Between the Main Domain and Subdomain at All?

Does PR flow like a river?

So does PR flow like a river to the sea or is it more like a dam to a lake?

So this was another question sent in to us by a client who wanted to better understand how the whole SEO thing works. In essence, what he wants to know is whether or not there is any relationship whatsoever between the PR rank of the main domain on your site (i.e. mysite.com) and subdomains (i.e. blog.mysite.com). Not mentioned but implied is also the question of subdirectories (i.e. mysite.com/blog).

Just What Is PR Anyway?

The first time I ever heard the term PR applied to websites, I thought it was referring to putting out news releases and getting your website mentioned in various kinds of media. In a way I was right, but I was also very, very wrong.

The kind of PR I was thinking of refers to “Public Relations” which has been around for decades. This is in essence the act of trying to get your company noticed by the public at large by non advertising means. In other words, by getting press interviews, by putting out news releases, running publicity stunts and all manner of other efforts to be noticed.

Now I say that I was in a way right because the PR we refer to in SEO is actually Page Rank. This refers to a value which Google attributes to particular websites or really pages (by the way, in spite of what you may think, it’s not named for the pages that it ranks. It is named for Larry Page, the cofounder of Google who came up with the algorithm initially) on the Internet.

Page rank can range from a 0 all the way to a 10. The vast, vast, vast majority of pages on the Internet rank a 0, meaning that they tend to have precious little value as a place to get a link from. Mind you, it’s not that they have no value whatsoever. It’s just that you need a whole heck of a lot of such links in order to equal the value of a link from a higher PR page.

There are also by contrast precious few PR10 pages on the Internet. These are pages which are referenced constantly and which pretty much everyone has heard of. The homepage of Google and Facebook for example are in fact PR10 pages.

Most web pages in fact which we develop links from tend to be in the solid range of PR rankings (anywhere from around 2-7) but they will not actually be from PR10 websites and anyone who tells you that they are going to offer you hundreds of such links is generally trying to pull a fast one on you.

The High School Analogy

PR is just like high school

Just as you don't want to be the geek who thinks the Harry Potter look goes well with the Tom Cruise look, you don't want a website which looks awkward and which nobody links to.

Now, I have used this analogy before to explain exactly why and how PR works, but it’s worth repeating here because it is extremely pertinent. In essence, SEO is a lot like being in high school. Your goal in high school, other than getting a good grade on your report card is generally to climb the social ladder.

This means that ideally, you want to be dating the captain of the football team or the head cheerleader, depending on who you are and that everyone knows who you are and considers you to be “cool” whatever that ephemeral concept actually means.

The way that you do this is by starting out with yourself. You dress nicely, you make sure that whatever it is that you’re wearing is in fashion (actually, I recently read in the New York Times that this year kids are taking it to new extremes which make me worry about the future of America, but that’s for another discussion entirely).

The next thing that you do is to try to make friends, preferably with the “cool” kids, but if not then with anyone you can find whom you can find some way to get an “in” with so that you will be considered to have been noticed.

Google’s Page rank in essence works the same way as this – it checks to see who you “know” and who knows you. If your page is linked to by lots and lots of high ranking website and or has thousands of links from lesser known websites, then your PR rank will be that much higher because you are considered to be one of the “cool” kids by association.

A Common Misconception about PR

Now before I get into answering the question above (which is slightly more complicated than you might imagine it to be initially), I need to make sure to dispel one of the common myths that people tend to cling to regarding Page rank.

Just because a particular website has a particular page rank (for example, our blog here at Quantum SEO Labs has a page rank of 3. However, if you dig down and find a random page in our blog such as this one, which I wrote recently has a Page rank of 0. This means that just because you have a business page on Facebook for example, it doesn’t mean that you have a PR10 link.

Now the thing is, many unscrupulous SEO “experts” (I use the term very loosely because these guys are nothing but crooks) will tell you that they get you links on very high PR sites, things like PR6-9 for example. However, what they don’t tell you is that your link will appear on a page with PR0 or even worse, with PRN/A (meaning the page wasn’t indexed and your link is completely worthless). Thus it’s important to work with an SEO expert who is reputable and knows what they’re doing.

Another Thing to Remember about PR

Google tends to be pretty darn mysterious in the way they do their rankings. We have seen on numerous occasions that many of our clients would manage to get pages well ranked even though they happen to have low PR rankings on these pages while other pages, which have a higher PR ranking would not in fact get ranked nearly as highly.

There are several reasons for this apparent anomaly. The first and most obvious reason is that Google’s algorithm is massively complex. While Larry Page and Eric Schmidt did develop the basics of it back when they were broke college students with nothing but a dream, the algorithm has been changed thousands upon thousands of times since then.

In most cases, the changes are fairly minor and have precious little impact on the way that the web works on what the SERPs say about a particular page. However, in other cases, such as the recent Penguin update, the changes are pretty big and affect massive numbers of websites. Thus PR is only one of a great many factors which determine where you will rank.

Another reason why the PR issue is not necessarily such a big deal is that while Google’s SERPs are updated on a daily basis, the PR of any given website is actually updated only once per quarter. This means that Google may well have dropped the PR rank of a given website in the interim, but you wouldn’t happen to know about that change for months.

Bottom line of this is that while PR does make a difference in the world of SEO, it’s not the be all end all and it should not actually be relied upon as a way to figure out whether or not a particular page is going to rank well or not.

One More Point about Page Rank

Just one more point I want to make about Page rank before I finally get to actually discussing the question that was mentioned above (yes, I really am getting to it). As SEO experts, as I mentioned, we tend to ignore PR and focus instead on the quality of the links that you get. We don’t ignore it for the links that we set up, but we do tend to ignore it when it comes to your own ranking.

In point of fact, there has been talk on and off that I’ve noticed over the years of various SEO people saying that Google was planning to phase out the whole concept altogether because it’s been so misunderstood. I personally don’t believe that this will occur, however it is definitely true that people tend to pay way too much attention to this and too little attention to other factors which make you rank well.

Now about that Question

Question about PR rankings

It's actually a bit more complicated than you might initially think.

Okay, now that we have the basics out of the way, let’s discuss the question above, which is actually much more complicated than it may seem at first. First of all, there is a bit of a difference from an SEO perspective between a subdomain and a subdirectory. I wrote about this recently and explained why we generally recommend that you keep your blog in a subdirectory.

As a general rule, Google does treat both subdomains and subdirectories as a pseudo separate website. In some cases, it really is (for example, if you use a service like WordPress.com – a terrible idea BTW if that’s your only blog, but you can read more about that in my previous post).

It used to be that Google treated the subdomain or subdirectory as an entirely separate entity, however a few years ago, they changed their algorithm and now it’s kind of a pseudo separate website. It’s also worth noting that even a truly separate website (i.e. one which has a completely separate domain name) on the same IP address is only treated as a pseudo separate site.

However, for the purposes of our discussion, in theory at least, the answer is no – PR doesn’t flow from the main site to the subpages, subdirectories, subdomains at all. However, there is a very big “but” involved here which we need to talk about.

The “But”

Ah that “but.” You see, even though the PR doesn’t naturally flow from one to the other, there is a flow of what we SEO folks call “link juice” from one site to another if there is a link between them. In essence, what this means is that if you were to create a link from your main page to a subpage (or subdomain or subdirectory) then it would actually provide you with a certain amount of PR flowing from one to the other.

This is actually why we always tell our clients that they need to have internal links, but that is a discussion for another day.

What I will say here however is that you should not completely and totally discount the value of a link from a PR0 page on a high PR website. This has nothing to do with the links and has more to do with the fact that high PR webpages tend to attract more visitors.

Even though you may not actually derive benefit from the PR flowing from the main domain down to the subdomain, people may well find your page on the site simply because there are so many people who actually spend the time to visit the site in question.

Bottom Line

The bottom line is, PR can flow from the main domain name to a subdomain or to a subdirectory. However, it will not flow unless you create the links to allow it to flow because Google will treat it, at least for these purposes as a completely separate entity and not as one big website.

It’s also important to note that while this is my understanding of how PR works, Google doesn’t actually make public exactly how it is that their system does its rankings.

Thus, while it’s generally known that for PR purposes, Google tend to treat the subdomain or subdirectory or subpage as a separate entity, it is possible that there is some minor amount of link juice which will flow to a subdomain from the PR of the main page. So don’t go ignoring your Facebook page just yet, even though it may technically not be a PR10 page and may really be just a PR0.