International organizations use a bewildering variety of voting rules–with different thresholds, weighting systems, veto points, and other rules that distribute influence unequally among participants. We provide a brief survey of the major voting systems, and show that all are controversial and unsatisfactory in various ways. While it is tempting to blame great powers or the weakness of international law for these problems, we argue that the root source is intellectual rather than political–the difficulty of designing a voting system that both allows efficient collective decisions and protects the legitimate interests of members. We show how a new type of voting system– quadratic voting–could in theory resolve these problems, and while it may be too new or unusual to implement any time soon, it provides insights into the defects of the existing systems.