Ever since Sen crystallized the logical conflict between the welfaristic value of the Pareto principle and the nonwelfaristic value of individual libertarian rights into what he christened the impossibility of a Paretian liberal , there have been many attempts in social choice theory to...

A random assignment is robust ex-post Pareto efficient whenever for any of its lottery decomposition, each deterministic assignment in its support is Pareto efficient. We show that ordinal efficiency implies robust ex-post Pareto efficiency while the reverse does not hold. We know that...