beyond what employers will demand may fuel global migration of health workforce, especially if the surplus workers have skills profiles that meet the demand from the countries facing health workforce shortage. Otherwise, these surplus workers will add to unemployment in their respective countries.

Table 5 compares the supply projections of health workers with the needs‐based projections of the number of health workers required to meet basic health services utilization targets as defined by WHO for the same 165 countries for which we have demand estimates (WHO 2016). By 2030, based on the need‐based model, the largest health worker shortage will occur in low and lower middle income countries, particularly in the Sub‐Saharan Africa and South Asia regions. Low income countries face a situation in which both the demand and supply curves for predicted health worker densities fall below the WHO need threshold. In these countries, increasing the supply of health workers to the WHO threshold level will not be sustainable via the market alone, since the demand generated in the labor market will not be sufficient to employ higher numbers of health workers.

In summary, trends in the predicted health worker demand, supply and needs by income level are illustrated in Figure 2. Growth in both demand for and supply of health workers is predicted to be the slowest in low income countries, and these are projected to remain significantly below the WHO SDG threshold of 4.45 workers per 1,000. As a result, these low income countries might experience a paradoxical situation in which they face shortage of health workers needed to provide basic health services, yet they will also face unemployed health workers due to the limited national capacity to employ the available supply of workers. Middle income countries are predicted to experience the largest increase in shortages over this time period, reaching 3.7 million workers in lower‐middle income countries and 11.9 million workers in upper middle income countries by 2030. Although these countries will generate sufficient demand for health workers that meet and exceed the WHO SDG threshold density, their challenges will be in producing sufficient numbers of qualified health workers to meet projected demand. The model predicts that high income countries would have a relatively balanced growth in both demand and supply of health workers. However, it should be pointed out that the supply projections used in this analysis used only the net increase in the supply of health workers, and did not take into account changes in the attrition and retirement rates of the health workers. Estimates for the European Union that take into account these workforce dynamics suggest that many high income countries will face substantial shortages of health workers by 2020 due to rapid aging of the current stock of health workers if the rate of production is not increased to compensate for anticipated higher exit rates (Buchan et al., 2014).

# **Policy Implications**

Policy makers must allocate resources and set priorities today based on expectations of future need and capacity to support health workers. Our projections of health worker demand show that predicted trends in the labor market will likely enable many countries to employ more 10