This paper intends to place the inertial-rules concept within the framework of Generalised Darwinism. We are talking of a specific kind of replicator that continues to persist across generations of interactors, even when the particular environment, to which it was suitable for, is meanwhile changed. Until a selective variation intervenes, this kind of rule survives and affects economic outcomes. The inertial rule should be meant as a tool of the economic disciplinary domain for which the validity of Generalized Darwinism is asserted. Empirical evidence is offered from a backward economy of the South of Italy, which may explain different levels of growth in different regions.