Technorati has changed its "authority" calculations

In the past, Technorati Authority was a simple number - the number of blogs linking to your website in the past 6 months. Now they have changed the calculation methodology:

• Authority is calculated based on a site’s linking behavior, categorization and other associated data over a short, finite period of time. A site’s authority may rapidly rise and fall depending on what the blogosphere is discussing at the moment, and how often a site produces content being referenced by other sites.
• The new Authority calculation differs from the past version, which measured linking behavior over a longer 6 month timeframe. Please note that links in blogrolls don’t count towards Authority, as they are not indicative of interest in relevant content; we stopped including blogroll links in August 2008.
• Authority is on a scale of 0-1000. 1000 is the highest possible authority.

They do not offer details of the methodology, presumably preferring to keep the process confidential so bloggers can't easily "game" the system.

In the past, we based Technorati Authority on six months of blogosphere data. Because most searches are looking for items less than a month old, we’re going to narrow that window in a similar way. In the past, because the data window was so long, Authority and the Top 100 lists it powered were relatively static. With the new algorithm, the resulting Authority will better reflect the fast-changing nature of the blogosphere. Its new inherent volatility will also show which blogs are rising and falling in authority, rewarding authors on posting frequency, context and linking behavior, as well as other data inputs.

The new numbers are wildly different from the old ones. I'm guessing that somehow they are incorporating the authority of the blogs that link to your blog as one of the determinative factors.

It will be interesting to see how the Weblog Awards rejigger their categories for small/midsize/large blogs, which used to be determined by Technorati Authority numbers.

Addendum 10/21: "Blog reactions" (links to your blog) are still not shown, but admin says "We'll be bringing back Blog Reactions (in an updated form) soon, so you will be able to see who's linking to you."

Re the sidebar badges being out of date: "I think these are in the works -- stay tuned."