The Hans Böckler Foundation has now published the study "Crowd Worker in Deutschland - an empirical study of the working environment on external crowdsourcing platforms". It has been published as Volume No. 323 in the Foundation's "Study" series. 

In it, the authors Prof. Dr. Jan Marco Leimeister, David Durward and Shkodran Zogaj from the Department of Information Systems at the University of Kassel investigate various topics in the field of crowdworking in Germany on the basis of a survey of 434 crowdworkers: Which groups of people offer their work on the various crowdsourcing platforms? How much time do they spend working in the crowd? What do they earn? What significance does crowd work have for their livelihood? How do they secure themselves socially? How satisfied are they? What do they want for their professional future?

More information on this study including download option can be foundhere http://www.boeckler.de/6299.htm?produkt=HBS-006421&chunk=1.