THE INTERACTING EFFECTS OF PRICES AND WEATHER ON POPULATION-CYCLES INA PREINDUSTRIAL COMMUNITY

The exogenous cycles and population dynamics of the community at Penri th, Cumbria, England, have been studied (1557-1812) using aggregative analysis, family reconstitution and time series analysis. This communi ty was living under marginal conditions for the first 200 years and th e evidence presented is of a homeostatic regime where famine, malnutri tion and epidemic disease acted to regulate the balance between resour ces and population size. This provides an ideal historic population fo r an investigation of the direct and indirect effects of malnutrition. Throughout the period studied, a short wavelength oscillation in grai n prices was apparently the major external factor that drove exogenous cycles in mortality, birth rate, and migration. In particular, the di fferent responses of children to variations in food supply are emphasi sed; fluctuations in poor nutrition correlated significantly with the variations in mortality rates for infants (probably indirectly during pregnancy and directly during the first year of life) and for young ch ildren (via susceptibility to lethal infectious diseases). Migratory m ovements contributed to the maintenance of homeostasis in the populati on dynamics. A medium wavelength cycle in low winter temperatures was associated with a rise in adult mortality which, in turn, promoted an influx of migrants into this saturated habitat. A model incorporating these interacting associations between vital events and exogenous cycl es is presented: grain prices were an important density-dependent fact or and constituted the major component of the negative feedback of thi s population and drove the exogenous, short wavelength mortality cycle s. Cycles of births and immigration provide a positive feedback for th e build-up of susceptibles and the initiation of smallpox epidemics an d increased population size.