There are generally three forms of aggregate supply (AS). They are:
- Short run aggregate supply (SRAS) — During the short-run, firms possess one fixed factor of production (usually capital). This does not however prevent outward shifts in the SRAS curve, which will result in increased output/real GDP at a given price. Therefore, a positive correlation between price level and output is shown by the SRAS curve.
- Long run aggregate supply (LRAS) — Over the long run, only capital, labour, and technology affect the LRAS in the macroeconomic model because at this point everything in the economy is assumed to be used optimally. In most situations, the LRAS is viewed as static because it shifts the slowest of the three. The LRAS is shown as perfectly vertical, reflecting economists' belief that changes in aggregate demand (AD) have an only temporary change on the economy's total output.
- Medium run aggregate supply (MRAS) — As an interim between SRAS and LRAS, the MRAS form slopes upward and reflects when capital as well as labor can change. More specifically, the Medium run aggregate supply is like this for three theoretical reasons, namely the Sticky-Wage Theory, the Sticky-Price Theory and the Misperception Theory. When graphing an aggregate supply and demand model, the MRAS is generally graphed after aggregate demand (AD), SRAS, and LRAS have been graphed, and then placed so that the equilibria occur at the same point. The MRAS curve is affected by capital, labor, technology, and wage rate.
An increase in aggregate demand shifts the AD curve rightward, bringing the equilibrium point horizontally along the SRAS until it reaches the new AD. This point is the short run equilibrium.
