The Price Level.
Neither the demand for money, the supply of money, nor the two together completely
explain the price level. If the nominal quantity of money supplied equals the quantity demanded, equation (1)
summarizes the relationship among several variables. Those variables are the nominal quantity of money, the
price level, and real income as well as all of the other factors that affect the demand for money and are reflected
in the factor of proportionality, k.
If real income, y, were constant and factors reflected in k other than real income also were constant, equation
(1) would provide a direct relationship between the nominal quantity of money and the price level. An informative
way of rewriting equation (1) is
P = k–1(M/y). (2)
This equation highlights the relationship between the price level and factors that determine it.7 It also makes
clear that the nominal quantity of money is not the only factor affecting the price level.
If real income were constant and other factors did not affect the demand for money or were constant, then
there would be a proportional relationship between the price level and the nominal quantity of money relative
to real income. If the nominal quantity of money M changed, then P would change by the same proportion
because k and y were constant.
While patently unrealistic, this supposition is a useful starting point for thinking about what has to be true
for the nominal quantity of money and the price level to be proportionally related. Further analysis and assumptions
about what is more or less important create a proportional connection between the nominal quantity of
money and the price level.
First, consider real income. Real income changes over time and affects the demand for money. The factors
that determine real income, though, are largely if not entirely unrelated to the demand for money and the supply
of money, especially over longer periods.8 The major factors affecting the growth of real income over time are
growth of resources available to produce goods and services and technological change. Printing money does not
create more labor or real capital to produce goods and services or affect technological change. Hence, at least over
longer periods, real income is independent of the nominal quantity of money and the price level. As a result, changes
in real income do affect the price level, but there is a proportional relationship between the price level and the
nominal quantity of money relative to real income.
If variation in the demand for money for reasons other than real income, indicated by the k in equations
(1) and (2), is relatively unimportant, then equation (2) indicates that the price level and money relative to real
income are proportionally related. There need not be such a close relationship between the price level and the
nominal quantity of money relative to income. If variation in the demand for money for reasons other than real
income is substantially more important than variation in the money supply relative to real income, this variation in
the demand for money can result in no observable relationship between the price level and money relative to
real income.9 Changes in the price level will be associated with changes in the demand for money, k in equations
(1) and (2), and not money relative to real income. The relative importance of variation in the supply of money
and the demand for money for explaining the price level is therefore an empirical issue.
Money and Prices in the United States since 1953. Chart 1 shows the relationship between the price level
and money relative to real income for the United States from the first quarter of 1953 through the end of 1997.10
The vertical axis uses a proportional scale for the values of money relative to real income and the price level.
With a proportional scale, the proportional and percentage changes in the price level and in money relative to
income are represented by the slopes of the respective lines. The inflation rate is represented by the slope of
the line for the price level. The growth rate of money relative to real income is represented by the slope of the
line for money relative to real income.
The average values of the price level and of money relative to income are set to 100 in Chart 1. As a result, the
graph shows the percentage deviations of the price level from its average and the percentage deviations of money
relative to real income from its average. Nothing in the construction of the graph forces any coincidence of the
lines. A strictly proportional relationship would be indicated by the coincidence of the two lines. A positive but
less than perfectly proportional relationship is indicated by the two lines’ general agreement in terms of direction
and rate of change.11