I did a search for "blog net earnings survey" and ended up with this post by Darren Rowse at www.problogger.net announcing the result of a poll they conducted asking their readers how much did they earn from Adsense in November 2005.
In Problogger's poll, they found out that in 2005, around 46% of those who responded earned less than $30 in November of that year, or less than $1 in a day, with the most number (27%) earning only less than $10 for the month. A small number of around 5% said they earned over $10,000. And that's in November of 2005! Around 19% said they were not using Adsense.
How true are the numbers today? Don't miss my next posts on this subject.