The long-run aggregate supply (LRAS) curve is depicted as a vertical line because it represents the potential output of an economy when all resources are fully employed. At this level, also known as potential GDP, the economy is producing at its maximum sustainable capacity. A simplified illustration is that regardless of changes in the overall price level, the economy can only produce a specific quantity of goods and services in the long run given its resources, technology, and institutions.
This vertical representation is significant because it highlights the classical dichotomy: in the long run, real variables (like output) are independent of nominal variables (like the price level). Fiscal and monetary policies can influence aggregate demand and, consequently, prices, but they cannot permanently shift the LRAS or sustainably increase long-run output. The position of the LRAS indicates the inherent productive capacity of the economy, representing a crucial benchmark for evaluating economic performance and guiding policy decisions. Historically, the understanding of this concept emerged from the development of classical economic thought and its refinements through neoclassical synthesis.
