Group strategyproofness in queueing models

We identify and characterize a natural and intuitive class of mechanisms called the k-pivotal mechanisms. The axioms used are efficiency, pairwise strategyproofness, equal treatment of equals and weak linearity. We also identify the subclass of these mechanisms which do not run a budget deficit at all profiles and the mechanism which runs the least budget surplus. We also show that while k-pivotal mechanisms are also weak group strategyproof, strong group strategyproofness and efficiency are incompatible.