Globally, there has been a recent surge in ‘citizens’ assemblies’1, which are a form of civic participation in which a panel of randomly selected constituents contributes to questions of policy. The random process for selecting this panel should satisfy two properties. First, it must produce a panel that is representative of the population. Second, in the spirit of democratic equality, individuals would ideally be selected to serve on this panel with equal probability2,3. However, in practice these desiderata are in tension owing to differential participation rates across subpopulations4,5. Here we apply ideas from fair division to develop selection algorithms that satisfy the two desiderata simultaneously to the greatest possible extent: our selection algorithms choose representative panels while selecting individuals with probabilities as close to equal as mathematically possible, for many metrics of ‘closeness to equality’. Our implementation of one such algorithm has already been used to select more than 40 citizens’ assemblies around the world. As we demonstrate using data from ten citizens’ assemblies, adopting our algorithm over a benchmark representing the previous state of the art leads to substantially fairer selection probabilities. By contributing a fairer, more principled and deployable algorithm, our work puts the practice of sortition on firmer foundations. Moreover, our work establishes citizens’ assemblies as a domain in which insights from the field of fair division can lead to high-impact applications.
In representative democracies, political representatives are usually selected by election. However, over the past 35 years, an alternative selection method has been gaining traction among political scientists2,6,7 and practitioners1,8,9,10: ‘sortition’, which is the random selection of representatives from the population. The chosen representatives form a panel—usually known as a citizens’ assembly—that convenes to deliberate on a policy question. (Such panels also go by other names; our work applies to all panels in the broader category of ‘deliberative minipublics’11.) Citizens’ assemblies are now being administered by more than 40 organizations in over 25 countries12; one of these organizations—the Sortition Foundation in the UK—recruited 29 panels in 2020. Although many citizens’ assemblies are initiated by civil-society organizations, they are also increasingly being commissioned by public authorities on municipal, regional, national and supranational levels1. Notably, since 2019, two Belgian regional parliaments have internally established permanent sortition bodies13,14. The growing use of citizens’ assemblies by governments is giving the decisions of these assemblies a more direct path to affecting policy. For example, two recent citizens’ assemblies commissioned by the national legislature of Ireland led to the legalization of same-sex marriage and abortion15.