Dr. Vijay and Dr. Milind, used 12,000+ Chitika Publishers Network Data for their Research [Earnings Data Included as Well]. They used Technoarti to get the rank of the blog. Some bloggers are estimated to earn 3 times the revenue from other sources [AdSense / YPN] than they earn from Chitika. [Chitika is more suitable for Product Review Blogs]
The top 5% of the blogs accounted for 50% of the revenues. You can read the entire report here.
A similar estimation research was conducted by Pinstorm and IAMAI to estimate the online advertising market in India using Google AdSense as the base and without actually obtaining data from Google.