Background: The paper is motivated by the need for improved social evaluation of prospective demographic change in order to better inform policies that are designed to reduce the very long-run costs of population ageing and to achieve sustainable economic development. Objective: What is the very long-run social value of a given demographic path? What is the value of changes in mortality, immigration, fertility, and labour force participation? How important are shorter-term demographic changes relative to very long-term effects in determining the social value of the demographic path? Methods: A new simulation method is applied for socially evaluating demographic paths, by separating a demographic path into a stable population component and a transition path component. Sensitivity analyses are conducted with respect to demographic assumptions, labour force participation assumptions, and consumption needs by age, returns to scale, and intergenerational value judgements. Results: The application to Australia shows the considerable social cost, in terms of the loss of discounted consumption per capita, of improvements in mortality and gains from higher immigration and increased participation. The effect of fertility, however, is very sensitive to assumptions about the age-specific consumption needs of the population and social value judgements about intergenerational equity. Conclusions: Our method socially evaluates the very long-run implications of specified constant fertility, mortality, and migration, giving consideration to both the transition path and the ultimate stable state. Mortality improvement is costly and higher immigration is beneficial. The impact of higher fertility is sensitive to assumptions about consumption needs and intergenerational equity.