Short and medium run effects of a fiscal expansion
We can use the ASAD model to look at the short and medium run effects of a fiscal expansion.
You can trace the effects of the fiscal expansion through a few of the short run models:
1. In the Keynesian Cross an increase in G shifts up the planned expenditure line, so you get a new equilibrium where planned expenditure (demand) = actual expenditure (output) at a higher level of output.
2. This means that the goods market comes into equilibrium at a higher level of output for all interest rates, so it is reflected in an outward shift of the IS curve.
3. An outward shift of the IS curve means that, keeping the LM curve constant, the goods and money markets come into equilibrium at a higher level of output in the ISLM model.
4. Anything that causes a higher level of equilibrium output in the ISLM model means the goods and money markets are coming into equilibrium at a higher level of output at all price levels, this is reflected in an outward shift of the AD curve.
Here we have started from a medium-run equilibrium in the ASAD with output at the natural level (Yn) and price expectations being level with actual prices. The AD curve has shifted out to the right. The effects are that we have got a higher equilibrium level of output, Y2, and that price expectations are now running below actual prices (Pe<P2). This is our short-run effect.
Now we think about what happens to the AS curve. The AS curve will take us back to the medium run, with the adjustment mechanism being price expectations. As price expectations are below actual prices, they will adjust upwards. When expected prices increase, the AS curve shifts upwards. Remember that in the medium run, output will be back at the natural level, Yn.
Now the AS curve has shifted upwards to take us back to medium run, we are at the natural level of output again and at a point where expected prices equal actual prices. The only difference is the price level is now higher. I have labelled P1 as the original equilibrium price level. We had a short run rise in prices from P1 to P2, before price expectations caught up with them, and then by the time expected prices had caught up with actual prices it was at P3.
What has really gone on here is that the fiscal expansion has stimulated output in the short run, which has put upward pressure on prices. When workers have realised that actual prices were ahead of the price expectations they based their last wage claims on, they will adjust their expectations upwards and reflect this in their next round of wage bargaining. The rising prices will be reflected in higher wages which will then increase firms’ costs, so firms will pass these costs onto consumers in higher prices. This is why the AS curve is shifting upwards, firms are charging higher prices for the same amount of output, so at all levels of Y, P is higher.
We can also look at the effects on interest rates by tracing out this story in the ISLM model.
Now in the medium run we will go back to the natural level of output, and the ASAD model tells us that it is the price mechanism that will get us there. In the ISLM model, changes in prices are reflected in shifts of the LM curve.
Higher prices will effectively mean a reduction of the real money stock, and so this will drive up the interest rate which brings the money market into equilibrium at all levels of output. This is an upwards shift of the LM curve. So the LM curve will shift up to get us back to the medium run where output is at Yn.
So now in the medium run we are back at Yn in terms of output, but have reached a new medium run equilibrium with a higher interest rate. The interest rate has risen from i1 to i2 in the short run, while output went from Yn to Y2, but then returned to a medium run level of output, Yn, with a higher equilibrium interest rate, i3.
So the conclusion from this ASAD and ISLM analysis is that a fiscal expansion will cause -
A rise in output, a rise in prices and a rise in interest rates in the short run.
No change in output, but a higher price level and higher level of interest rates, in the medium run.