Day 219 Aggregate demand curve and the inflation rate

Aggregate demand curve and the inflation rate

The aggregate demand curve is used to describe the relation between the output (aggregate spending) and the inflation rate. It is downward sloping due to the higher inflation rate will create uncertainties for expenditure, reduce the wealth holding and enormously reduce the export value. 

Changes in exogenous factors that are independent from output or real interest rate will shift the aggregate demand curve. In addition, addition, the tighter monetary policy that set interest higher for each given rate of inflation will reduce the aggregate demand and shift it to the left. The aggregate supply is based on the short/long-run inflation rate. In short-term, we assume that firms do not adjust their price corresponding to the demand, so the SRAS is a horizontal line. The long-run aggregate supply indicates the economy potential output. The short-run equilibrium indicates the actual output level under the current inflation rate, the economy tends to correct itself when there is an output gap. Thus, if there is an expansionary gap, firms will raise the price to match the excess demand. It there is a contractionary gap, firms will cut the price as to sell more. As a result, a result, giving enough period of time, the economy itself will eliminate the output gap and achieve long-run equilibrium. By studying the AD-AS model, the source of inflation is clear. It can be caused by the increase in exogenous components that shift the AD curve to the right. That will create an expansionary gap, so the inflation will rise as stated before. Another source of inflation change is the inflation shock, which adverse inflation shock raises the current inflation rate, and favorable inflation shock reduces the inflation rate. The adverse inflation shock will bring the inflation rate up, therefore the reserve bank may choose to ease its monetary policy to eliminate the recessionary output gap. There is another type of shock to potential output, that will decrease the long-run aggregate supply, hence create an expansionary gap. As a consequence, the inflation rate will increase till the new long-run equilibrium. Both of the adverse shock in inflation and the shock to potential output are the aggregate supply shock, which will reduce output and increase inflation. For the purpose of inflation control, the central may choose to tighter their monetary police before an anticipated rise in inflation. This will deliberately create a recessionary gap with shifting the AD curve to the left, thereby the inflation rate can be expected to fall. 

Generally, the public’s expectation and the inflation rate are mutually affected. The higher the predicted inflation, the more proportion of wages people will ask to rise. This will make the firm to raise the price to cover the cost, so the inflation will increase. And vice versa.