Secular stagnation is an economic theory suggesting that advanced economies may experience prolonged periods of low growth, low interest rates, and high unemployment. This phenomenon occurs when there is insufficient demand for goods and services, often due to factors like demographic changes, income inequality, and technological advancements that reduce the need for labor. The term was popularized by economist Larry Summers, who argued that without significant investment opportunities, economies may struggle to achieve sustainable growth. This stagnation can lead to challenges in monetary policy, as traditional tools may become less effective in stimulating the economy.