We argue that, in order to explain the relative strengths of our reasons to contribute to different collective endeavours, approaches to the ethics of collective action must understand the strengths of our reasons to make a given contribution as proportional to its expected benefits, or its chances of bringing about benefits in proportion to their magnitudes. The view that most clearly meets this proportionality requirement is the expected consequences approach, which identifies our reasons to perform an act with its expected (...) benefits. We contend that views other than the expected consequences approach must similarly proportion the expected degrees of what they take to be reason-giving features of a contribution – such as its virtuousness, appropriate expression, support by considerations of fairness, or helping without making a difference – to the contribution’s expected benefits. The proportionality requirement explains why we should spend more time participating in strategic social, political, and labour movement activities, while avoiding unproductive conflicts and merely performative activities. We conclude that the proportionality requirement, and the ability of views other than the expected consequences approach to meet it, are important for thinking and communicating about the ethics of collective action in ways that are simultaneously most compelling and most strategic. (shrink)