Preferential Attachment in Feeds

April 18th, 2006

The size of the blogosphere continues to double every six months” as per the latest quarterly report on the State of the Blogosphere by David Sifry. According to this report there are 33.5 Million weblogs and many of these are activly posting. Last year there was a post by Jim Lanzone from Ask on which feeds matter? According to Bloglines/Ask in July 2005 there were about 1.12 Million feeds that really matter, which is based on the feeds subscribed by all the users on Bloglines. A study of the feeds on bloglines in April 2005 showed that there were about 32,415 public subscribers and their feeds accounted for 1,059,140 public feed subscriptions.

We collected similar data of the publicly listed users on bloglines. From last year, the number of publicly listed subscribers have increased to 82,428 users (2.5 times that of last year) and there are 1,833,913 listed feeds (~ 1.7 times) on the Bloglines site. Hence even though the blogosphere is almost doubling every six months, the number of feeds that “really matter” probably doubles roughly every year. Inspite of it, it may still be only a small fraction of the blogosphere.

This leads me to think that there is some preferential attatchment for feeds. A new user who joins bloglines would subscribe to some of the feeds from the long tail (belonging to friends and based on interest) but most would tend to also subscribe to feeds that are already popular (such as slashdot or other top popular feeds).

Number of subscribers per feed

There is also an inherent limit on the amount of information that a user can keep track of at any given time. To study this we show the number of feeds subscribed by the publicly listed users on bloglines.

feeds per user

From the graph it can be observed that although there are some users who monitor more than 5k feeds (which might not be real users but programs using bloglines API), a majority of users are normal users who subscribe to the blogs and news feeds that they want to follow regularly. Mostly, these users have somewhere between 30-100 feeds that they monitor. This might explain the deviation of the graph from that of a typical power law curve.

To summarize:

  • The blogosphere continues to grow as does the number of people who follow blogs.
  • While this is still a rough estimate, the number of feeds that really matter is a very small fraction of the entire blogosphere.
  • The number of feeds that really matter doubles each year as opposed to the size of the blogosphere, which doubles every 6 months.
  • Most users tend to follow a relatively modest number of feeds.