This research paper examines the short-run and long-run effects of population growth on economic growth and the variations in these effects across countries with different levels of development. Using data published by the World Bank and The Maddison Project (2020), a fixed effects model is conducted to examine the relationship between population growth and economic growth in approximately 160 countries over the span of 170 years. The results of this analysis find that lower income countries and countries with lower levels of human capital experience the greatest increases in economic growth due to population growth. Additionally, past population growth explains more of the variation in current population growth which points to strong long-term effects of population growth. These results support the economic theory of convergence whereby developing countries experience faster economic growth than developed countries and the notion that population growth can lead to greater innovative capacities which drive economic growth.