All stratified (e.g., non-egalitarian) societies have groups of individuals that do not produce, but still receive a 'cut' of the social surplus. Note-- this question is not how elderly or children receive a 'cut', but those in the upper strata or elites convince the direct producers (lower strata) to turn over a part of their surplus to them (e.g., via taxes, tribute, etc.). How does Diamond argue that these 'privileged' individuals manage to convince/compel productive members of society to give them part of their surplus and hence maintain the social stratification?