I somehow missed this question from the Open Questions post and I can’t help but answer it.

From Adsenser

I loved your SEO empire post. But I was wondering how much effect does a lot of links from a lot of indexed pages from the same domain have? I always thought that the search engines looked mainly at the number of different domain linking to you. Can you give some more info on this? Or do you use these pages to link to a lot of different domains?

This is a fantastic opener for a conversation on sitewide outbound links affects on other sites as well as the site itself. Which has been long debated but never cleared up, not because its too complicated just because theres so many myths its hard to work the fact from the fiction. To be clear in my answer I’m going to refer to the site giving the link as the “host site” and the site receiving the link as the “target site.” Just so I don’t have to play around with too much terminology.

The entire explanation of why sitewide links, main page links, subpage links, and reciprocal links work is based off a simple SEO law called Diminishing Values. It basically states that for every link whether it be recipricol, innerlink, or outbound link there is some form of consequence. Also, for every inbound link, innerlink accepted or reciprocal link there is a benefit.

SEO Law of Diminishing Values Diminishing Values = sum(benefits) > sum(consequences)

The need for the sum of the benefits to be greater than the sum of the consequences is essential because, as mentioned in my SEO Empire post there can’t be a negative relevancy for a site in relationship to a term. For example lets take the niche of cars. There’s a theoretical mass of car blogs. For the sake of the example we’ll say there are several thousand blogs on the subject of cars. Something in the industry happens that stirs all the bloggers such as SEMA having a car show or something. So all these car blogs blog about SEMA’s new car show coming out and give it a link. If these outbound links caused a consequence greater or equal to the valued benefit given to SEMA than all these blogs would drop in value as per the topic, cars. Thus the mass affect would be that of a negative relevancy, therefore sites with no relevancy but contain topic links would by all theory rank higher than the general census of on topic sites.

So the notion of an outbound link diminishing your sites value in equal proportion is just complete bubkiss and obviously not the way things actually work. Even if it was true and there was a compensation for on site SEO when an event in a niche happens the site hosting the event wouldn’t just rise in the rankings it would propel everyone else downwards causing more turbulence in the SERPS than what happens in actuality with just their site rising. It’s just simple SEO Theory 101, but sadly a lot of people believe it. There’s also a lot of sites that absolutely won’t link to any sites within their topic in fear that their rankings will suddenly plummet the moment they do. They’re under the greedy impression that they’re somehow hording their link value and that is in some way benefiting them. So with the assumption that an outbound link gives much more value to its target than it diminishes from its host everything in a sense balances out and outbound links become much less scary. This of course in no way says that the consequence to the host is a diminishment of any sort. It’s entire consequence could be 0 or as a lot of other people believe +X (some people think on topic outbound links actually adds to your sites relevancy). I haven’t personally seen one of my sites go up in rank after adding an outbound link but I’m open to the idea or to the future of the concept being reality.

I Practice What I Preach The Law of Diminishing Values is one of the reasons why BlueHatSEO is one of the only SEO blogs that has all dofollow comments as well as top commentators plugin on every page. Your comments will not hurt my rankings..I’ll say that one more time Your comments will not hurt my rankings. Whewww I feel better

Back To The Question Before we get into the meat of the question we’ll take a small scale example that we should all know the answer to. Q: If a host site writes an automated link exchange script that automatically does thousands of link exchanges and puts those links on a single subpage and all the target sites also have their link exchange page setup the same way on a subpage. Will the host site gain in value?

A: I’ll tell you straight up from personal experience. Yes it does. It’s simple to test if you don’t believe me go for it yourself

Now we’ll move up to a much larger scale with a specific on topic example using sitewide links. Q: If you own two 100k+ page lyric sites with lots of inbound links and very good indexing ratios, will putting a sitewide link to the other site on both raise both in value or keep them both the same?

A: Also from my personal experience, yes both will not only raise in value but they will skyrocket in value by in the upwards of 50% which can result in much higher rankings. Likewise this example can be done with any niche and any two large sites. Cross promote them with sitewide links between the two and see what happens. The results shouldn’t be surprising.

Now, on the large scale to the meat of the question. Q: If these two lyrics site cross compared all their inbound links from other sites and managed to get all the sites that link to lyric site A to also link to lyric site B to the point at which each increased in links by 100k (same as the number of increased links would of been with a sitewide link between the two) would both sites increase in value more-so than if they did the sitewide link instead?

A: Yes absolutely. This is a bit harder to test, but if you’ve been building an SEO Empire and each site’s inbound links are from your own sites than it becomes quite a bit easier to test and I’m certain you’ll find the results the same as I did.

Conclusion On a 1:1 ratio on a generalized population of relevant links vs non-relevant inbound links from separate domains/sites are still more effective than a sidewide link of the same magnitude. However! A sitewide link does benefit both sites to a very high degree. Just not to the degree that lots of other sites can accomplish.

Sorry that question took so long to answer. I didn’t just want to give you a blank and blunt answer. I wanted to actually answer it with logic and a reasoning that hopefully leads to an understanding of the ever so important WHY.