We analyse the computational complexity of three problems in judgment aggregation:
(1) computing a collective judgment from a profile of individual judgments (the winner
determination problem); (2) deciding whether a given agent can influence the outcome
of a judgment aggregation procedure in her favour by reporting insincere judgments (the
strategic manipulation problem); and (3) deciding whether a given judgment aggregation
scenario is guaranteed to result in a logically consistent outcome, independently from what
the judgments supplied by the individuals are (the problem of the safety of the agenda).
We provide results both for specific aggregation procedures (the quota rules, the premisebased
procedure, and a distance-based procedure) and for classes of aggregation procedures
characterised in terms of fundamental axioms.