Compete site comparison graphs, Unique Visitors and Visits of the biggest microstock agencies in the last year (Compete estimates U.S. Internet Traffic). On July, for the first time, United States iStock traffic data are lower than Shutterstock, Dreamstime, 123rf ones. More traffic stats on Microstock agencies page, with the strong rising of Depositphotos and Photodune.
I write about the stock photo and microstock industry since 2006 on my several online-magazines. My goal for MyStockPhoto is to teach photographers and stock photographers how to sell more photos and earn money with their photography hobby.
Depositphotos is really show very good results. Sales are bigger than at Bigstock.