Aggregate supply (AS) is a core macroeconomic concept describing the relationship between the economy-wide price level and the total real output that firms collectively produce. It is typically depicted as an upward-sloping curve in the short run and a vertical line at potential output in the long run.
Economists usually distinguish two timeframes:
- Short-run aggregate supply (SRAS): Slopes upward because wages, contracts, and some input prices are sticky. When the general price level rises faster than costs, profit margins expand and firms increase output. Standard explanations include the sticky-wage model, sticky-price model, and misperceptions model associated with Robert Lucas.
- Long-run aggregate supply (LRAS): Vertical at the economy's potential output (sometimes called the natural rate of output). In the long run, output is determined by the supply of labor and capital, technology, and institutions—not by the price level. This reflects the classical dichotomy and the natural rate hypothesis advanced by Milton Friedman and Edmund Phelps in the late 1960s.
Shifters of AS include changes in input prices (notably oil and wages), productivity and technology, the size and skill of the labor force, the capital stock, taxation and regulation, and expectations of future prices. A leftward shift of SRAS combined with rising prices produces stagflation, famously observed after the 1973 OPEC oil embargo.
Aggregate supply interacts with aggregate demand (AD) in the AD–AS framework, which is the workhorse model used in most introductory and intermediate macroeconomics textbooks (e.g., Mankiw, Blanchard) and by central banks to explain inflation, output gaps, and the effects of monetary and fiscal policy. Supply-side policies—such as deregulation, tax reform, education investment, and infrastructure spending—aim to shift LRAS rightward, raising sustainable output without generating inflationary pressure.
For policy analysts and MUN delegates working on economic committees (ECOFIN, UNCTAD), AS analysis is essential when evaluating responses to commodity shocks, productivity slowdowns, and structural reform proposals.
Example
After Russia's 2022 invasion of Ukraine drove up European energy and grain prices, eurozone short-run aggregate supply shifted leftward, contributing to inflation peaking at 10.6% in October 2022.
Frequently asked questions
SRAS slopes upward because wages and some prices are sticky, so higher price levels temporarily raise output. LRAS is vertical at potential output, determined by labor, capital, and technology rather than prices.
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