This paper provides an axiomatic approach to the problem of measuring the informationcontained in opportunity sets. In many choice situations, the items that can be selectedfrom an opportunity set (the objects of choice) do not coincide with the consequencesthey induce (the objects a...

We analyze the rationalizability of variable-population social-choice functions in a welfaristframework. It is shown that xed-population rationalizability and a weakening ofcongruence together are necessary and suffcient for rational choice, given a plausible dominanceproperty that prevents the...