--- - |2 It is axiomatic among scholars of participatory democracy that consensus‐based decision making is inefficient, yet no study has systematically assessed that claim. This article examines the efficiency of consensus decision making in 12 social movement groups from the German autonomous and nonviolence movements. Data were analyzed from 62 semistructured interviews regarding how long it took each group to make a typical decision and what types of decisions were the easiest and most difficult to make. A measure of inclusiveness was included to determine whether efficiency was attained by silencing dissent. Most decisions were made in less than two hours. Factors were identified that distinguished more and less efficient groups. - The Sociological Quarterly, Volume 57, Issue 1, Page 36-70, Winter 2016.