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Home > AP Courses and Exams > Course Home Pages > Nominal or Real? Understanding Interest Rates in AP Macroeconomics

Nominal or Real? Understanding Interest Rates in AP Macroeconomics

by Peggy Pride
St. Louis University High School
St. Louis, Missouri

Understanding the Underlying Concepts
From 1980 through 1984, inflation plunged from 9.2 to 3.7 percent. However, because the nominal rates on Treasury Bills fell only from 11.5 to 9.6 percent over the same period, the real, inflation-adjusted returns on Treasury Bills actually rose from 2.3 to 5.9 percent. During one of the 1984 campaign debates, incumbent President Reagan boasted that his administration had successfully lowered interest rates. A few minutes later, his challenger Walter Mondale insisted that interest rates were at their highest point in decades. While these seemingly contradictory claims confused most viewers, economic students around the world knew both candidates were correct. Nominal rates were
down -- just as Reagan had claimed -- while real rates were up -- just as Mondale had countered.
-- Robert J. Stonebraker, "Is It Real... or Is It Nominal?"
This puzzling quote helps one comprehend the confusion about a question on the 2005 AP Macroeconomics Exam, which challenged students to discriminate between nominal and real interest rates. Here I will attempt to explain the question's underlying concepts and how they relate to the money market and the loanable funds market.
  2005 AP Macroeconomics Free-Response Exam Questions

Students in AP Macroeconomics become aware of the terms nominal and real when they study the measurement tools of the economy and the gross domestic product (GDP). Nominal GDP is expressed in current dollars and based on prices when the goods were produced. Real GDP is expressed in constant dollars and is adjusted up or down to reflect changes in the price level. The GDP deflator introduces students to the concept of an index and helps them distinguish between the two values. Another strand of the idea is nominal wages -- the dollar amount earned -- and real wages -- the purchasing power of those dollars.

Later in the semester, nominal and real interest rates are introduced. The nominal rate of interest is stated as a percentage and is the price paid for the use of money. The real rate of interest, also stated as a percentage, is the constant or inflation-adjusted value. It is the percentage increase in purchasing power that the borrower expects to pay back to the lender. So, nominal rate = real rate + expected rate of inflation, or, expressed another way, real interest rate = nominal rate - expected rate of inflation.

Critical Information for Investors
The real rate of interest is crucial in making investment decisions. Business firms want to know the true cost of borrowing for investment. If inflation is positive, which it generally is, then the real interest rate is lower than the nominal interest rate. If we have deflation, and the inflation rate is negative, then the real interest rate will be larger. 

Nominal rates are determined in the money market. Money demanded and money supplied determines the equilibrium interest rate. The demand curve will slope downward. The vertical axis (interest rate) is the opportunity cost of holding money. An increase in the interest rate raises the cost of holding money and reduces the quantity of money demanded. A decrease in the interest rate reduces the cost of holding money and increases the quantity of money demanded.

Price-level changes will affect the demand curve in the money market diagram. At higher price levels, more money is needed for transactions, so people will choose to hold a greater quantity of money. A higher price level means that the demand curve moves to the right, increasing the nominal interest rate if the supply of money is constant.

The supply of money is vertical no matter what the interest rate is on the vertical axis, since the Federal Reserve controls the supply of money through its monetary policy tools.

The Money Market

 




Money Market -- Nominal Interest Rates
Easy Money Policy -- Federal Reserve
When the Federal Reserve adopts an easy money policy, the supply of money moves to the right, and the interest rate falls. This stimulates investment and interest-sensitive consumption, which increases the aggregate demand. Price levels rise, while real output increases.

The Money Market



Tight Money Policy -- Federal Reserve
When the Federal Reserve adopts a tight money policy, the supply of money moves to the left, and the interest rate rises. This discourages investment and interest-sensitive consumption, which decreases the aggregate demand. Price levels fall, while real output decreases.

The Money Market



Loanable Funds Market -- Real Interest Rates
Real interest rates are determined in the loanable funds market. The loanable funds theory of interest explains the interest rate in terms of the demand and supply of funds available for lending. Irving Fisher (1867-1947) first distinguished explicitly between the nominal and real rates of interest. His contribution was so noteworthy that an increase in the nominal interest rate in anticipation of inflation is known as the "Fisher effect." Equilibrium occurs where the supply (savings) intersects the demand (investment, consumption). Movement to equilibrium is the process of determining the real interest rate in the economy. Note the use of the label r on the vertical axis. This helps to remind us that this graphical model gives us the real interest rate. The supply of loanable funds is all income that people have chosen to save and lend out rather than use for their own consumption. The demand for loanable funds comes from households and firms that wish to borrow to make investments.

Loanable Funds Market

 

 

At times of deficit, the government can join this market on the demand side. A change in investment or consumption decisions moves the demand curve, while changes in savings decisions move the supply curve. Government policies that influence the loanable funds market include government budget deficits and fiscal polices that influence taxes and investment. These policy decisions can move either the demand or the supply curve. When a government decreases the tax on interest income, the incentive for households to save at any given interest rate increases. The curve for the supply of loanable funds shifts to the right, and the result is that the equilibrium interest rate decreases as the quantity of loanable funds increases.

Loanable Funds Market

 



When government gives an investment tax credit for new equipment, this fiscal policy action increases the incentive to borrow. The demand for loanable funds curve shifts to the right, and the result is that the equilibrium real interest rate and quantity of loanable funds both increase.

Loanable Funds Market

 



When government deficit-spends, there are two views to consider. In one view, private saving is reduced (as funds are diverted to the purchase of government securities), and the supply curve moves to the left. In the other view, government demand (seeking loanable funds to finance debt) is added to the private demand in the market, and the demand curve moves to the right.

Supply View of Government -- Deficit Financing
When governments borrow to finance budget deficits, this reduces the supply of loanable funds made available to finance investment by households and firms. This is a shift in private saving away from the loanable funds market. The supply curve moves to the left; the result is that the equilibrium interest rate increases, and the quantity of loanable funds decreases.

Loanable Funds Market



In the other view, government demand for loanable funds to finance debt moves the demand curve to the right. This second view is the clear illustration of the "crowding out effect": the higher real interest rate discourages private borrowing by businesses and consumers. You can see the loss of investment and interest-sensitive consumption spending on the graph below. In theory, this leads to lower private investment and consumption and a decrease in aggregate demand, causing real GDP to decline with a lower price level. Deficit spending as a tool of fiscal policy is usually directed to stabilization in terms of moving the economy to a higher level of growth in GDP. When government moves into the market for loanable funds, new demand is generated. The demand for loanable funds curve shifts to the right, and the demand now comes from two sources, private and government (DP + G). The result is that the equilibrium real interest rate and quantity of loanable funds both increase. But note that the quantity (Q) of loanable funds from the private market is reduced, and there is a loss of private investment and consumption (I and C) spending.

Loanable Funds Market

 

 

A point to remember is that, according to the Keynesian model, deficit spending will lead to a short-term increase in real GDP. This increase in the equilibrium level of loanable funds does lead to crowding out of private investment and consumption, but the graph also shows an increase in the total quantity of loanable funds exchanged. This means that the government is spending the borrowed dollars on something -- toilet seats, hammers, roads, dams, bridges, and so on. What is not clear from the graph is whether public investment is as effective as private investment, and ultimately, that is what determines the long-term impact of the deficit spending.

Interest rates are important for the economy, as lower rates can pave the road to economic growth. These two models make a distinction between the sources of funds that create the supply curve. Remember that in the money market graph earlier in this article, the supply of money is determined by the actions of the Federal Reserve, while in the loanable funds market the supply of funds is based primarily on the savings of the private sector. Teachers will serve their students best if they distinguish between these two markets and help them to understand the concept of nominal and real interest rates. Using the questions from previous years' AP Exams for drill and practice will help to reinforce your lesson. Good luck!


Sources
Mankiw, Gregory N. Principles of Economics. 3rd ed. Mason, Ohio: Thomson/South-Western, 2004.

McConnell, Campbell R., and Stanley L. Brue. Economics: Principles, Problems, and Policies. 15th ed. New York: McGraw-Hill, 2002.

Stonebraker, Robert J. "Is It Real... or Is It Nominal?" 1997, modified May 2003. http://faculty.winthrop.edu/stonebrakerr/Econ216/realint.htm.

Peggy Pride has taught at St. Louis University High School since August 1981. Peggy has been a microeconomics Question Leader at the annual AP Reading since 2001. She served for five years on the AP Economics Development Committee. She is currently AP Central's content adviser for AP Economics.


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