A CGD Working Paper with George Yang. This paper explores the potential implications of a declining absolute labor force on economic outcomes. It explores key macroeconomic variables during periods of negative and positive prime age (15-65) population growth (PAPG). These variables include 10-year bond yields, consumer price indices, female labor force participation, GDP, government expenditures, government revenue, and stock returns. We find effects may include lower economic growth, declining government revenues, flat or declining labor force participation, and lower investment returns. As negative PAPG is spreading worldwide, this portends a less favorable economic outlook.