Abstract: A new hypothesis regarding the role of rare earth dopants in improving the lifetime of multilayer capacitors with base metal electrodes is presented. The hypothesis is based on the experimental findings, which have shown that the site occupancy of the important dopants is a function of the overall A/B ratio in the perovskite dielectric material. The main assumption is that deviation from A/B stoichiometry significantly controls the mobility of oxygen vacancies along the grain boundaries.