NCERT Book Class 12 Economics (Macroeconomics) Chapter 4 Determination Of Income and Employment

Chapter 4
Chapter 4
Determination of Income and
Employment
We have so far talked about the national income, price level,
rate of interest etc. in an ad hoc manner – without
investigating the forces that govern their values. The basic
objective of macroeconomics is to develop theoretical tools,
called models, capable of describing the processes which
determine the values of these variables. Specifically, the
models attempt to provide theoretical explanation to
questions such as what causes periods of slow growth or
recessions in the economy, or increment in the price level,
or a rise in unemployment. It is difficult to account for all
the variables at the same time. Thus, when we concentrate
on the determination of a particular variable, we must hold
the values of all other variables constant. This is a stylisation
typical of almost any theoretical exercise and is called the
assumption of ceteris paribus, which literally means ‘other
things remaining equal’. You can think of the procedure as
follows – in order to solve for the values of two variables x
and y from two equations, we solve for one variable, say x,
in terms of y from one equation first, and then substitute
this value into the other equation to obtain the complete
solution. We apply the same method in the analysis of the
macroeconomic system.
In this chapter we deal with the determination of National
Income under the assumption of fixed price of final goods
and constant rate of interest in the economy. The
theoretical model used in this chapter is based on the theory
given by John Maynard Keynes.

4.1 AGGREGATE DEMAND AND ITS COMPONENTS
In the chapter on National Income Accounting, we have
come across terms like consumption, investment, or the
total output of final goods and services in an economy (GDP).
These terms have dual connotations. In Chapter 2 they
were used in the accounting sense – denoting actual values
of these items as measured by the activities within the
economy in a certain year. We call these actual or
accounting values ex post measures of these items.
These terms, however, can be used with a different
connotation. Consumption may denote not what people
have actually consumed in a given year, but what they