These increases are massive compared to the typical abstract views and downloads these papers get- one blog post in Freakonomics is equivalent to 3 years of abstract views! However, only a minority of the readers click through-we estimate 1-2% of readers of the more popular blogs click on the links to view the abstracts, and 4% on a blog like Chris Blattman that likely has a more specialized (research-focused) readership.
And finally, I am very much a part of the results of this study. McKenzie and Ozler sent a survey around to graduate students in economics about the degree to which they read blogs, use blogs to find out about papers and write their own blogs. Since I answer YES to all of these questions, I feel like I personally contributed to the lovely graphical results.