Rogers-Castro Migration Schedule

The Rogers-Castro migration schedule is a parametric model that captures the remarkably regular way migration rates vary with age. Across countries and eras, the probability of moving is high in infancy, falls through childhood, surges to a sharp peak in the early adult labour-force years, and often shows a secondary bump around retirement. Andrei Rogers and Luis Castro, working at the International Institute for Applied Systems Analysis, formalized this regularity in their 1981 monograph as a sum of exponential and double-exponential curves whose parameters have direct demographic meaning. The simplest version uses seven parameters to describe the childhood decline and the labour-force peak; nine- and eleven-parameter extensions add retirement and post-retirement components. Fitting the schedule by nonlinear least squares smooths noisy age-specific rates, allows missing or sparse data to be filled in, and yields interpretable indices — the mean age of the labour-force peak, its sharpness, and the spacing between the childhood and labour curves. The result is a compact, comparable summary of an entire age profile of migration that feeds directly into multiregional projection and the analysis of migration selectivity.