BlogAds, arguably the leading blog advertising network, has released their 2006 Blog Reader survey results
The median political blog reader is a 43 year old man with an annual family income of $80,000. He reads 6 blogs a day for 10 hours a week. 39% have post-graduate degrees. 70% have contributed to a campaign. 69% have bought music, 87% have bought books. 58% say blogs are “extremely useful” sources of information. 52% leave comments on other people’s blogs. Just 18% of political blog readers have their own blogs. (As you’ll see, that’s a lot lower than in other blogospheres.) Of these, 53% blog to keep track of their own ideas, 50% to let off steam, 36% to influence public opinion.
This is quite different than the February Harris Interactive survey of 2000 blog readers which came up with the following result:
Young males dominate blog readership. 21 percent of people who reported reading a blog within the past 30 days were males, ages 18-29.
An audience of young males aged 18-29 is probably not the best demographic for advertisers.. but a 43 year old man with an $80,000 income could very well be. Perhaps this is why DailyKos charges $5k a week for a blogad on their site.
The survey goes on to show the various breakdowns in some of the more popular blog communities & genres and illustrates the radical differences between the varying genres.