Tuesday, May 08, 2007

A Suggestion for Technorati's Blog Authority Ranking Algorithm

Technorati's Director of Product Development, Dorion Carroll, announced on May 5, 2007, that henceforth the firm will rank blogs by Authority rather than "N blogs link here" and "X links from Y blogs." Technorati determines Authority by the number of links from unique sites during the preceding 180 days. 

I've added a Technorati Authority widget below the LINQ and Entity Framework popularity graphs.

The change made no appreciable difference in the OakLeaf System blog's ranking, which was Authority = 94, Rank = 45,767, and 218 links when this post was written. The main blog page has had a constant Google PageRank of 0.5 for many months.

I believe Technorati needs to use a different algorithm if they're going to claim to rank Authority. If the Authority of a blog is based on the number of inbound links from unique sites, the measure should take into account the Authority of each linking site. That is, a link from a blog such as Michael Arrington's TechCrunch (Authority = 18,372, Rank = 8, Links = 128,985) or Mary Jo Foley's All About Microsoft blog (Authority = 1,431, Rank = 1,110, Links = 3,974) should carry more weight than links from Splogs or LinkBlogs with no authority. For starters, I'd recommend not counting links from blogs with Authority < 1.

Summing the authority—rather than the number—of each unique linked blog won't work because doing so would add excessive weight to Authority. However, a root that weighs inbound links from the top blog say 10 times those of a blog with Authority = 1 might be appropriate. The top-ranked blog is Engadget with Authority = 27,553 and Links = 595,691.

Using the 0.228th power (~4.4th root) of Authority (Authority^0.228) = 10.08 for Authority = 27,553 provides the following Authority multipliers with the four blog examples in this post and more common lower Authorities:

Blog   Authority   Multiplier
Engadget 27,553 10.1
TechCruch 18,372 9.2
All About Microsoft 1,431 5.2
OakLeaf Systems 94 2.8
Many Blogs 10 1.7
More Blogs 5 1.4
Most Blogs 2 1.2
Lowest-ranking Blog Counted 1 1.0

Obviously, rankings would change substantially because the Authority of blogs' inbound links would increase, so the exponent might need to be recalculated frequently when transitioning to the new method. Limiting the Authority refresh frequency would aid in reducing the resources devoted to the calculations.

What's your opinion?

Technorati tags: , , ,


Brian Salchert said...

I agree with you. I also wonder why the last 180-days limit.
If you don't mind, I have a number of questions:
1. Why the popularity-contest approach to worth?
2. What exactly is a unique link?
I have 2 blogs. The major one was started 11/03/06 and a tech site
has linked to a math page in it, but there has never been any
indication about that at Technorati.
This blog of mine has an authority of 5.
My other blog has no authority, but
yesterday an important literary blog linked to it via its blogroll.
06/22/07 was the date I began it.
3. How long does it take for T-- to recognize a change?
4. Should I create links between my blogs?
So far I have just mentioned each in the other's About Me.
5. Why is it visitor counters count a blog owner's visits?
Thank you for your information:
I found your site by doing a how Technorati determines authority
Brian A. J. Salchert

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