The problem with the IS-LM model
The starting point of the Aggregate Demand - Aggregate Supply or AD-AS model is an assumption in the IS-LM model (and in the cross model) that limits its usefulness. This is the assumption that if firms where to choose the profit maximizing quantity of L (LOPT), they would produce more than the aggregate demand. In the IS-LM, YOPT > YD must hold as discussed in section Aggregate supply.
To realize why this is a problem in the IS-LM model, we gradually increase the aggregate demand byincreasing G. We can illustrate the process using figure 12.6 in Section The Labor Market
The purpose of this chapter is to try to explain the growth in GDP. The models in this chapter are very different from the rest of the models in this book as they use only the production function and factors of production to explain growth.
An important macroeconomic variable is the total amount of labor that is used in a certain time period. The amount of labor and the amount of capital are important explanatory variables for production and GDP. Another reason for the importance of the amount of labor is that it is related to the unemployment rate – a macroeconomic variable which is clearly important.
The Keynesian model
In this chapter we will look at the Keynesian cross model. This model is a simple version of what we call the ”complete Keynesian model” or simply the Keynesian model. The Keynesian model has as its origin the writings of John Maynard Keynes in the 1930s, particularly the book ”The general theory of Employment, Interest, and Money”.
The neo-classical synthesis is a synthesis of the classical model and the Keynesian model. In short, it states that the Keynesian model is correct in the short run while the classical analysis is correct in the long run. Let us consider a concrete example. According to the Keynesian model, an increase in G will increase Y and reduce unemployment.