'This study provides governments of all countries an opportunity to start rethinking their policies on migration, workforces and economic development to address the challenges presented by demographic change.' Christopher Murray, who led the research.

'Continued global population growth through the century is no longer the most likely trajectory for the world's population,' says IHME Director Dr. The new study also predicts huge shifts in the global age structure, with an estimated 2.37 billion individuals over 65 years globally in 2100, compared with 1.7 billion under 20 years, underscoring the need for liberal immigration policies in countries with significantly declining working age populations. The new population forecasts contrast to projections of 'continuing global growth' by the United Nations Population Division, and highlight the huge challenges to economic growth of a shrinking workforce, the high burden on health and social support systems of an aging population, and the impact on global power linked to shifts in world population. This means that in these countries populations will decline unless low fertility is compensated by immigration. Using novel methods for forecasting mortality, fertility, and migration, the researchers from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington's School of Medicine estimate that by 2100, 183 of 195 countries will have total fertility rates (TFR), which represent the average number of children a woman delivers over her lifetime, below replacement level of 2.1 births per woman. The modelling research uses data from the Global Burden of Disease Study 2017 to project future global, regional, and national population.

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