Large-Scale Simulation Models in Population and Development: What Use to Planners?

Large-scale simulation modeling is a highly visible arrival on the population and development scene-one that commands increasing resources year by year. In 1967 only a few modestsized existed, and only one, the General Electric Company's TEMPO-I, was in wide use. By 1975 at least a dozen large models were in various stages of construction and operation; more were in the planning stage. Each of these models consists of a detailed, recursive computer program for the simulation of long-term development. The focus is on population, and the idea is to give developing country planners a means to test alternative policy choices and to deepen their insight into the future impact of present decisions. This paper examines the thinking behind the current economic-demographic models, and presents a critical assessment of their potential use to development planners. Although in its present form, systems-based and computer-intensive, large-scale simulation modeling in population and development has been in existence less than ten years, the origins go further back-at least to the 1958 Coale-Hoover model for evaluating the impact of a hypothetical fertility reduction in India.' That this model became the ancestor of so many computer-based analyses was somewhat unintentional: Coale and Hoover argued the case for fertility reduction verbally, through careful, nuanced analysis, in the main body of their book; the formal model is added almost as an afterthought in the back pages-in 1958, systems thinking did not dominate economic analysis. This early study spawned a number of similar formulations during the 1960s, these efforts gradually becoming less