While electoral gender quotas are rapidly disseminating all over the world, they are also meeting with fierce resistance. A closer look at quota debates reveals that a considerable number of arguments for and against quotas take the form of predictions of the impact of quotas. This article identifies a number of key predictions from the quota debate in relation to three dimensions: descriptive representation, substantive representation and symbolic representation. Through examples from the growing quota research, the article discusses how nine selected pairs of predictions have been or could be tested empirically. By this we hope to move the discussion of quotas away from the present deadlock between quota proponents and opponents. A central argument made is that the differences in research results do not only derive from variations between the countries, but also from the use of disparate criteria of evaluation. The article points to the need for clarification and the development of common concepts and criteria.