In this article we ask whether it is possible to evaluate the efficiency of an online knowledge production project to determine its position in the life-cycle of projects and to identify factors that affect efficiency. To assess efficiency, we used the Data Envelopment Analysis (DEA) modelling methodology, applying it to data from Wikipedia, studying more than 30 Wikipedia language projects over three years. We showed that if the main Wikipedia projects were indeed less efficient that smaller ones, corrected by the decreasing return to scale phenomenon, they were quite as efficient as the other projects.