SOCIAL STRUCTURE OF CONTRIBUTIONS TO WIKIPEDIA * Andreea Daniela Gorbatai Harvard University Wyss Hall 203D Harvard Business School Boston, MA 02163 agorbatai@hbs.edu Miko aj Jan Piskorski Harvard University Morgan Hall 243 Harvard Business School Boston, MA 02163 Tel. (617) 495-6099 mpiskorski@hbs.edu * John Sheridan helped us assemble the dataset. Division of Research at Harvard Business School provided financial support. All errors are ours.