Google has a post explaining the addition of subscriber numbers to its Google Reader service.
There's been a lot of discussion this weekend about the subscriber counts that have recently appeared in Reader's search results. Leaderboards have been drawn up, numbers are being compared and in some cases there's confusion as to how these numbers compare with other subscriber metrics. Additionally, we've made changes (some as recently as today) as to how counts are being calculated. This is probably going to be pretty boring unless you're a feed publisher, but we thought it would be best to explain things a bit. Here are the various numbers you may come across, and what they all mean:
Google subscriber counts: These numbers include subscribers across all Google services, including Reader, iGoogle, and Orkut. You can see them in Reader's feed search results (pictured below) and the Google Webmaster Tools. Additionally, our crawler reports them to the publisher each time we fetch the feed. Reader's feed search was recently showing stale and incomplete data, but as of today (October 15) the numbers should be the same everywhere.
Mashable notes that feeds that have been included in one of the feed bundles on Google Reader tend to have the highest subscriber figures. That's probably true with any news reader that offers bundles. People are more likely to add one of the bundles which auto-subscribes them to all the feeds in the bundle. However, these readers won't necessarily become regular readers of all the feeds contained in the bundle - they may never even read a single one of the feeds. Still it would sure be nice to have your feed offered in one of the bundles. Mashable says the best way for that to happen is "by striking a deal with the feedreader company or being friends with the owner." Some of the same feeds have been bundled on Google Reader for quite a while. It would be nice if Google Reader and some of the other feed bundlers would mix it up a little bit and give other feeds a chance to be King for a while.