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Changes in the genetic constitution of the Tristan da Cunha population, measured in terms of the probable ancestral contributions to the genepool at a series of points in time and previously summarised visually, are assessed quantitatively. The distance statistics Z and 6 are measured between decade years and years of special interest. The effects of the bottlenecks in population size were to enhance the rapidity of approach to the present constitution. Both Z and θ give the general impression of a population steadily changing in its genetic constitution, but with increasing stability in later decades.