Consumer Price Index – Definition

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Consumer Price Index Definition

The Consumer Price Index (CPI) examines the aggregate prices of basket of consumer goods and services in an economy. Basket of goods and services refer to products commonly purchased by individuals and households such as food, gas, clothing, transportation, health care services and others.

CPI measures changes of price in these products and services. It measures the cost of living as well as inflation and deflation of prices in an economy. It is a statistical method for detecting the purchase power of people in a country, it also measures divergence of price rates of a collection of goods and services.

As used in the United States, the Consumer Price Index (CPI) measures changes in price of a basket of goods and services consumed by households. The United States Bureau of Labor Statistics (BLS) calculates CPI every month and has been doing this since 1913.

The Consumer Price Index as reported by BLS measures changes in prices of goods and services and how this affect the cost of living in the United States. Items such as savings and investments are not reported by BLS under CPI, the variation in price for goods and services experienced by non-residents may be excluded.

How CPI is Used

CPI is used as a statistical measure for identifying periods of inflation or deflation in a country. The Consumer Price Index also indicates the cost of living and the effects of governmental policy on prices of basket of goods and services that people pay for. CPI also reflect variations in prices of goods and services which enable prompt decisions from appropriate agencies.

CPI is also essential in determining the purchasing power of individuals. CPI also helps to determine the eligibility of individuals to social security and other government assistance. The BLS also links cost-of-living adjustments of people on Social Security to Consumer Price Index.

The Consumer Price Index measures price variation of a basket of consumer goods and services, that is, changes in prices of products and services. Excise taxes that have effect on prices are captured when the BLS gives CPI reports. There are eight items that sum up to a basket of consumer goods and services, these are;

  • Foods and beverages
  • Transportation
  • Housing
  • Education and communications
  • Clothing apparel
  • Health care
  • Recreation
  • Other goods and services.

There are specific categories of people that are taken into consideration when calculating or reporting CPI, these include professionals, poor citizens, self-employed and unemployed and retirees. CPI report does not cover the armed forces, inmates, mentally deranged persons, visitors, and rural population.

Calculating CPI

The Consumer Price Index can be calculated on a single item in the basket of consumer goods and services for a given year. The formula for calculating CPI for a single item is;

Cost of Market Basket in Given Year

CPI = _______________________________   X 100

Cost of Market Basket in

Base Year

The BLS records quite a large number of items every month, in order to accurately measure CPI for a given year. BLS records are derived from information gotten from all providers of goods and services that make up the basket.

Types of CPI

The Consumer Price Index is categorized into two types, they are;

  • The Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W).
  • The Consumer Price Index for Urban Consumers (CPI-U)

The first type of CPI measures the variation in prices of goods and services of households whose incomes make up more than one-half from wage occupations. CPI-W covers about 28% of the United State’s population. BLS focused on this between 1913 and 1977. This type of CPI also show variation in cost of benefits that individuals under social security receive.

CPI-U on the other hand covers a wide population, it represents about 88% of the population. Individuals in metropolitan areas, poor people, professionals, retirees, self-employed and employed, urban wage earners and clerical workers are represented.

CPI Regional Data

Aside from doing an overall calculation, BLS calculates the Consumer Price Index based on regions. The four census regions and the major metro areas are reported by BLS. About 80,000 items that are reported by BLS each month are broken into four census regions, the West, South, Northeast and Midwest.

Furthermore, CPI reports are also broken down into Los Angeles-Riverside-Orange County, Chicago-Gary-Kenosha, and New York-Northern NJ-Long Island. These are the three major metropolitan areas in the United States. Reports are also made in additional 11 metro areas every other month and 13 metro areas semi-annually.

Reference for “Consumer Price Indexes (CPI)

Academic Research articles for “Consumer Price Indexes (CPI)”

An overview of experimental US consumer price indexes, Moulton, B. R., & Stewart, K. J. (1999). Journal of Business & Economic Statistics, 17(2), 141-151.

Seasonal baskets in consumer price indexes, Baldwin, A. (1990). Journal of Official Statistics, 6(3), 251.

Measurement biases in consumer price indexes, White, A. G. (1999). International Statistical Review, 67(3), 301-325.

Consumer price indexes: methods for quality and variety change, Greenlees, J. (2000). Statistical Journal of the United Nations Economic Commission for Europe, 17(1), 59-74.

Post‐Laspeyres: The Case for a New Formula for Compiling Consumer Price Indexes, Armknecht, P., & Silver, M. (2014). Review of Income and Wealth, 60(2), 225-244.

Constructing household specific consumer price indexes: An analysis of different techniques and methods, Cage, R. A., Garner, T., & Ruiz-Castillo, J. (2002).

Consumer price indexes and demand functions, Konüs, A. A. (1958). Revue de l’Institut International de Statistique, 29-36.

New consumer price indexes by size of city, Bahr, R. C., Meiners, M. R., & Nakayama, T. (1972). Monthly Lab. Rev., 95, 3.

Plutocratic and democratic consumer price indexes: An estimation of a democratic index for Italy 1995-2005, Chelli, F., & Mattioli, E. (2007).

The British and the United States Consumer Price Indexes, Hurwitz, A., & Blackman, W. (1957). The British and the United States Consumer Price Indexes. Monthly Lab. Rev., 80, 475.

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