The degree of change in the hierarchy of occupations over long periods is the focus of this paper. Our concern is with the mechanism by which the hierarchy changes. Taxable wealth of incumbents of detailed occupations from 1789 Philadelphia is related to income data from the last three dicennial censuses. Several models of how change might occur are evaluated. We conclude that (1) change in occupational reward differentials is slower than previous estimates, and (2) the first-order causal mechanism by which change in the hierarchy has been presumed to take place is implausible. We also note within-occupation variability in assets of approximately the same magnitude in the two periods.