Explore the connection between the economic indicators and real-world issues. These lessons typically can be done in one class period.


Consumer Price Index (CPI), Inflation, Real Gross Domestic Product (GDP), Unemployment

Current Key Economic Indicators

as of November 30, -0001

Goals of the Case Study

The goals of the Inflation Case Studies are to provide teachers and students:

  • access to easily understood, timely interpretations of monthly announcements of rate of change in prices in the U.S. economy;
  • descriptions of major issues surrounding the data announcements;
  • brief analyses of historical perspectives;
  • questions and activities to use to reinforce and develop understanding of relevant concepts; and
  • a list of publications and resources that may benefit classroom teachers and students interested in exploring inflation.

Information for Teachers

All paragraphs in italics will not appear in the student version of the inflation case study. The original press release can be found at

This lesson uses several charts and tables. You may use these files to create student reproducables or overhead transparencies for use in your classroom.


The consumer price index (CPI) during the month of December decreased by minus .1 percent (one-tenth of one percent). The rate of increase in the consumer price index over the past twelve months has been 3.4 percent.

In December, the core consumer price index, which excludes energy and food prices, increased by .2 percent (two-tenths of one percent). The core index has increased by 2.2 percent over the last twelve months.

[The core index excludes changes in food and energy prices. Thus if the CPI decreased and the core index increased, it must be that food or energy prices decreased. (In fact, energy prices decreased at a rapid rate (-2.2 percent) and food prices increased by .2 percent.)]

A follow-up discussion question might be to ask what the relationship between the two measures has been over the last 12 months. Ask students to explain.

[CPI has increased by 3.4 percent and the core by 2.2 percent over the last 12 months. Thus, food and energy prices together must have increased by more than the prices of all other goods. Energy prices have been the cause - a very large increase of 17.1 percent over the last 12 months.]

Definitions of Inflation

Inflation is a continual increase in the overall level of prices. It is an increase in average prices that lasts at least a few months. The most widely reported measurement of inflation is the consumer price index (CPI). The CPI measures the cost of a fixed set of goods relative to the cost of those same goods in a previous month or year. Changes in the prices of those goods approximate changes in the overall level of prices paid by consumers.

The core consumer price index is the average price of the same set of goods and services, without including food and energy prices, relative to the price of the set without food and energy prices in a previous month or year.

Data Trends

In March, the consumer price index increased by .4 percent, after increasing .1 percent in February. In March, energy prices increased once again. Price indexes for transportation and apparel also rose.

The annual rate of change over the last three months was an increase of 4.3 percent and over the last 12 months, an increase of 3.4 percent. Annual inflation rates from 2002 through 2005 were 2.4, 1.9, 3.3 and 3.4 percent.

This is only slightly higher than recent months, but we should be cautious about placing too much emphasis on any one month change.

The core rate of inflation (increased by .3 percent in March) represents changes in the consumer price index without the influences of changes in the prices of food and energy, which can fluctuate widely from month to month. The increased March index compares to .1 and .2 percent increases in the core rate of inflation in each of the previous six months. Core prices increased more slowly in the last three months than the overall index due to rises in prices of energy. The annual rate of decrease in prices of energy over the last three months was 21.8 percent.

Extra attention is given by forecasters to the core index as it tends to show more lasting trends in prices. This month's results provide some evidence that the increase in energy prices over the last several years has not significantly influenced rates of increases in all other prices. Still the rapid rise in energy prices may eventually have a significant effect on all other prices in the economy.

Graph 1

Figure 1 shows recent inflation data reported for each month. It is obvious that the monthly inflation figures change a great deal from one month to the next. However, the trend has been an increasing trend over the last five months. It is however difficult to tell what the trend over a longer period of time has been.

Graph 2

Figure 2 shows annual rates of inflation from the 1970s to now. Compared to the rates of inflation in the 1970s and much of the 1980s, the current rate of inflation is low. Few observers would describe the most recent rates, prior to this month, as high and they are not, when compared to those of the past thirty years. However, the recent rates have been increasing and that has caused some concern. See the most recent Federal Reserve case study and the exercises at the end of this case.

The Consumer Price Index

The seasonally adjusted consumer price index in March was 199.8. The price index was equal to 100 during the period from 1982 to 1984. The appropriate interpretation of the index is that prices in the market basket of goods and services purchased by the typical consumer increased from the 1982-1984 period to March, 2006 by 99.8 percent. A typical consumer good that cost one dollar in 1983 now costs $2.00.

Inflation is announced and reported in newspapers and television news as percentage changes in the CPI on a monthly basis. For example, the CPI in March was 199.8, compared to 199.1 in February. The increase in prices from February to March was (199.9 - 199.1) / 199.1 = .004. That means a monthly inflation rate of .4 percent.

To convert this into an approximate annual rate, you can simply multiply by 12. This provides us an annual inflation rate of (.4) (12) = 4.8 percent.

Table 1
Month Price Level Monthly Inflation Rate
March 199.8
199.8 - 199.1 = -.004 or - .4%

February 199.1

How the CPI is Calculated

Assume that there are only three goods (instead of goods and services in over 200 categories in the actual calculation) included in the typical consumer's purchases and, in the base or the original year, the goods had prices of $10.00, $20.00, and $30.00. The typical consumer purchased ten of each good.

In the current year, the goods' prices are $11, $24, and $33. Consumers now purchase 12, 8, and 11 of each good.

The CPI for the current year would be the quantities purchased in the market basket in the base year (ten of each good) times their prices in the current year divided by the quantities purchased in the market basket in the base year times their prices in the base year.

Thus [ (10 x $11) + (10 x $24) + (10 x $33)] / [( 10 x $10) + (10 x $20) + (10 x $30)] = $680 / $600 = 1.133. That is, prices in the current year are 1.133 times the prices in the original year. Prices have increased on average by 13.3 percent. The quantities are the base year quantities in both the numerator and the denominator.

By convention, the indexes are multiplied by 100 and reported as 113.3 instead of 1.133.

The base year index simply divides the prices in the base year (times the quantities in the base year) by the prices in base year (times the quantities in the base year). The base-year index then is 1.00; or multiplied by 100 equals 100.

How the CPI Data are collected

The Bureau of Labor Statistics samples the purchases of households representing 87 percent of the population. The consumer price index measures prices of goods and services in a market basket of goods and services that is intended to be representative of a typical consumer's purchases. Forty-one percent of the market basket is made up of goods that consumers purchase. The other fifty-nine percent includes services.

Goods and services sampled include food, clothing, housing, gasoline, other transportation prices, medical, dental, and legal services and hundreds of other retail goods and services. Taxes associated with the purchases are included. Each item is weighted in the average according to its share of the spending of the households included in the sample. Almost 80,000 prices in 87 urban areas across the country are sampled by Bureau of Labor Statistics professionals. Visits and phone calls are made to thousands of households and thousands of retail stores and offices. For more information on the Bureau of Labor Statistics, visit .

A Market Basket of Goods and Services

The Consumer Price Index measures prices of goods and services in a market basket of goods and services that is intended to be representative of a typical consumer's purchases. The relative importance of each of the categories of goods and services that included in the market basket are as follows.

Housing 42 % Recreation 6 %
Transportation 17 % Education and communication 6 %
Food and beverages 15 % Clothing 4 %
Medical care 6 % Other goods and services 4 %

Prices are collected through phone interviews and visits in almost 90 cities around the country. Almost 25,000 grocery stores, clothing stores, service stations, hospitals, and other retail stores are included. Fifty thousand families are interviewed.

For more information on the Bureau of Labor Statistics, visit .

CPI Interactive Exercise

Have your students answer the following multiple choice question:

[Teachers - The correct answer is increased. There are two primary ways to make the calculation. Prices have almost doubled. Income has more than doubled. Thus, real income has increased as prices have increased by less than nominal (using current prices) income.

A second method is that one could divide the current nominal income by 1.998 to get the current income in 1983 dollars. That is the real income. The result is that the current real income is $22,523. Thus real income has increased from $20,000 to $22,523]

CPI Interactive Activity

Have your students answer the following multiple choice question:

[Teachers - The correct answer is increased. Again there are two ways to arrive at the answer. Prices increased by 5 percent. GDP increased by 10 percent. Therefore, real GDP increased by 5 percent.

A more exact calculation is to calculate real GDP in both cases. In the first year, real GDP equals $10 trillion / 2.00 = $5 trillion in the base year's dollars. In the second year, real GDP equals $11 trillion / 2.1 = $5.24 trillion.]

Causes of Inflation


Over short periods of time, inflation can be caused by increases in costs or increases in spending. Inflation resulting from an increase in aggregate demand or total spending is called demand-pull inflation . Increases in demand , particularly if production in the economy is near the full-employment level of real GDP, pull up prices. It is not just rising spending. If spending is increasing more rapidly than the capacity to produce, there will be upward pressure on prices.

Inflation can also be caused by increases in costs of major inputs used throughout the economy. This type of inflation is often described as cost-push inflation . Increases in costs push prices up. The most common recent examples are inflationary periods caused largely by increases in the price of oil. Or if employers and employees begin to expect inflation, costs and prices will begin to rise as a result.

Over longer periods of time, that is, over periods of many months or years, inflation is caused by growth in the supply of money that is above and beyond the growth in the demand for money.

Inflation, in the short run and when caused by changes in demand, has an inverse relationship with unemployment. If spending is rising faster than capacity to produce, unemployment is likely to be falling and demand-pull inflation increasing. If spending is rising more slowly than capacity to produce, unemployment will be rising and there will be little demand-pull inflation.

That relationship disappears when inflation is primarily caused by increases in costs. Unemployment and inflation can then rise simultaneously.

Other Measures of Inflation

The GDP price index (sometimes referred to as the implicit price deflator). The GDP price index is an index of prices of all goods and services included in the gross domestic product. The index is a measure that is broader than the consumer price index.

The producer price index. This index measures prices at the wholesale or producer level. It can act as a leading indicator of inflation facing consumers. If the prices producers are charging are increasing, it is likely that consumers will eventually be faced with higher prices for good they buy at retail stores.


Have your students do the following assessment activity: