Chapter 19 Population dynamics: Equilibrium disequilibrium and consequences of fluctuations This chapter discusses the possibility of long run economic demographic equilibrium examines empirical evidence bearing on the key relationships hypothesized to establish equilibriumthe preventive check the positive check and a depressing effect of population growth on real wages reflecting diminishing returns to labor considers the nature of shocks to the equilibrium system both short run and longer runincluding historical examples from Europe. The chapter also presents the economic consequences of demographic fluctuations for savings consumer demand labor supply and related variables. The concept of equilibrium is important for understanding the broad sweep of history and economicdemographic equilibration leads to statistical traps that are a danger even for the visual interpretation of simple plots of historical data series because leadlag relations are often misleading across long cycles. Economicdemographic equilibrium requires that population growth encounters negative feedback of some kind. Fluctuations in the rate of population growth and in the population age distribution can potentially have large effects on the macroeconomy.