This paper presents an index that measures reviewer contribution to editorial processes of scholarly journals. Following a metaphor of ranking algorithms in sports tournaments, we created an index that considers reviewers on different context-specific dimensions, i.e., report delivery time, the length of the report and the alignment of recommendations to editorial decisions. To test the index, we used a dataset of peer review in a multi-disciplinary journal, including 544 reviewers on 606 submissions in six years. Although limited by sample size, the test showed that the index identifies outstanding contributors and weak performing reviewers efficiently. Our index is flexible, contemplates extensions and could be incorporated into available scholarly journal management tools. It can assist editors in rewarding high performing reviewers and managing editorial turnover. (C) 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC