In the fair division problem, the Pareto rule is known to satisfy stability properties under variation in the number of agents. We prove that the Equal Income Walrasian rule is its only subrule which is both stable and horizontally equitable.
Maniquet, F. (1996). Horizontal equity and stability when the number of agents is variable in the fair division problem. Economics Letters. https://doi.org/10.1016/0165-1765(95)00718-0