Difference Between CPI and RPI

Edited by Diffzy | Updated on: April 30, 2023


Difference Between CPI and RPI

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The CPI and RPI are the most frequently employed methods of measuring inflation. However, it is challenging to distinguish between the two indices since they both calculate inflation using a basket of products. While the Retail Price Index (RPI) tracks changes in retail economic output prices, the Consumer Price Index (CPI), which is projected, uses the average cost of economic output purchased by consumers as a foundation. The primary distinction between the consumer price index (CPI) and the retail pricing index (RPI) is that the former includes mortgage interest payments while the latter removes them.

Inflation is a sustained rise in the average price of goods and services throughout an economy. Therefore, an increase in inflation would suggest a decline in the currency's buying power. By increasing policy rates like the Repo Rate vs. Bank Rate, the Cash Reserve Ratio, and the Statutory Liquidity Ratio, the Reserve Bank aims to reduce inflation. Producer Price Indexes (PPI), Retail Price Index (RPI), and other metrics are used to determine inflation.


The cost of needs is gauged by the Retail Prices Index (RPI) and housing expenses like council tax and mortgage interest payments to determine the inflation rate. It employs arithmetic that divides the total number of things by the cost of all the items added together. The cost of hundreds of things we frequently purchase is measured to create the Consumer Prices Index (CPI), which does not include housing expenses. The inflation rate is then calculated using a geometric mean, which involves multiplying the prices of all the things by one another and taking their nth root, where n is the total number of items. The critical distinction between these two approaches is that the RPI almost always equals or exceeds the CPI; it is typically 1% higher than the CPI. Additionally, it is said that the CPI "better reflects changes in consumer spending habits relative to changes in the price of goods and services" (Office for National Statistics).

Many think simply utilizing the CPI would be preferable as it offers a more accurate representation of how inflation impacts expenditure. However, adapting to the CPI for all computations might make some people's situations worse. For instance, recipients of state pensions and benefits and those who get income from savings bonds may notice a decrease in their payments. In addition, the case for the new CPIH, which is currently slightly below the CPI and is computed using the same geometric mean as the CPI but also incorporates a measure of owner occupier's housing expenses, is rising.

Difference Between CPI And RPI in Tabular Form

Parameters Of Comparison CPI RPI
Definition The Consumer Price Index assesses price changes customers pay for a set basket of goods and services. A representative basket of products and services is used to determine the difference in retail price for the RPI, a consumer-inflation measure.
Use of Mean It employs the geometric mean. It uses the arithmetic mean.
Macroeconomic Relevance The CPI is a crucial instrument for assessing price stability and is often regarded as an indicator of inflation. RPI is not a method used by the Bank of England's Monetary Policy Committee to calculate inflation.
Uses Geometric mean Arithmetic mean
Housing Cost When calculating the index, housing costs are excluded. Included in the housing cost are mortgage interest payments and building insurance.
Housing costs Excluded Included
Elements Food, beverages, tobacco, fuel and light, housing, clothing, bedding, footwear, and other items are included in the market basket. Additionally included are salary contracts and government employees' dearness allowances. The RPI determines the cost of the retail goods and services basket. In addition, housing expenses, such as mortgage interest payments, are also taken into account by the RPI.
The date of introduction The CPI was introduced after the First World War when prices significantly increased. RPI was first computed in 1947 after being implemented in the U.K.

What Is CPI?

The Consumer Price Index (CPI) measures changes in the value of consumer goods and services purchased by households. Housing, clothes, bedding, food, drinks, tobacco, fuel, and light, as well as other footwear, are the five main components of the CPI. To calculate the index, the prices of the representative goods are gathered regularly. In addition, the actual worth of salaries, wages, and pensions can be used as an index by the CPI to measure price growth. The CPI is a popular macroeconomic inflation measure used by the RBI to monitor price stability.

A representative basket of products and services is used to calculate the Consumer Price Index; It monitors the long-term trend of consumer pricing changes. The CPI is the most commonly cited indicator of inflation, closely followed by other indicators utilized by policymakers, the financial sector, companies, and consumers. The widely used CPI is based on an index that accounts for 93% of the population of the United States. At the same time, cost-of-living adjustments to government benefits are made using a similar index that accounts for wage earners and clerical employees. The CPI is based on around 94,000 price quotations from about 23,000 retail and service businesses and 43,000 rental housing units. Housing rentals are utilized to calculate the change in shelter expenses, including those for owner-occupied housing; it accounts for almost one-third of the CPI.

Use of the Consumer Price Index (CPI)

The Federal Reserve and other participants in the financial market frequently use the CPI to adjust their monetary policies and monitor inflation. In addition, the CPI is used by both businesses and individuals to make intelligent financial decisions. For example, CPI is frequently considered when negotiating salaries since it tracks changes in consumer purchasing power. In addition, the CPI and its components are employed as a deflator for other economic indicators, such as retail sales and hourly/weekly wages, to distinguish between change reflecting fundamental change and change in prices. Federal payments to the roughly 70 million Americans receiving Social Security and Supplemental Security Income (SSI) benefits are impacted by cost-of-living adjustments (COLAs) based on the CPI. Additionally, they apply to federal pension benefits, school food programs, and tax rates.

Calculating CPI

The Bureau of Labor Statistics calc the CPI each month using a sample of 94,000 prices. To determine the overall price change, the index for each good or service is weighted according to its share of recent consumer expenditure. The substitution impact, which occurs as customers divert spending away from goods whose prices are rising relative to other interests, is also considered in the calculation. The CPI also takes into account improvements in product features and quality. Both seasonal adjustments and no modifications are given for the figures.

What Is RPI?

RPI, or retail price index, is an abbreviation. Calculating a market basket of retail products and services price fluctuations is a statistical process. It was initially presented as a compensation index in 1947. The Office of National Statistics releases a monthly report on the inflation rate in the United Kingdom. The organization's yearly rate is used as a benchmark to modify allowances, pensions, salaries, and wages that are inflation-indexed. The RPI uses a set basket of consumer goods and services to track price variations over time. The significance of the things determines their weight. The U.K.'s Office of National Statistics calculates and publishes a price index called the Retail Price Index (RPI). For statistical reasons, the official U.K. inflation rate is not the RPI because it is an older inflation indicator. However, RPI is still a cost escalation factor in wage contract negotiations and government transfer payments.

Interpretation Of the Retail Price Index (RPI)

The Retail Price Index (RPI), a more traditional measure of inflation, is still reported since it is used to determine the cost of living and wage growth. Still, it is not regarded as the government's official inflation rate. The Cost of Living Index was substantially replaced by the RPI when it was first computed in June 1947. It previously served as the primary official indicator of inflation. But in reality, the consumer prices index (CPI) now substantially fulfills that function. A new index called RPIJ was published in 2013 after a consultation on ways to improve the RPI revealed that the RPI's production methodology did not adhere to international standards.RPI was, after that, no longer categorized by ONS as a "national statistic." However, ONS will keep calculating RPI among other inflation indexes to give a reliable historical inflation time series. For firms liable to corporation tax in the U.K., the index factors are still employed to account for inflation in capital gains for inclusion in the tax computation.

Calculation Of RPI

It determines each product's weight and computes its proportion concerning its importance to the household budget. Then, the weighted cost is calculated by multiplying the weights by the individual item's price. Finally, the Carli and Dutot indices calculate the RPI as the arithmetic mean.

Main Difference Between CPI And RPI in Points

  • The data, known as the Consumer Price Index, looks at consumer price changes for a market basket of goods and services. The differential in the retail price of a comprehensive basket of goods and services is determined by the Retail Price Index, a consumer inflation indicator.
  • The geometric mean is used by CPI to determine the difference between the current and prior prices. On the other hand, RPI employs an arithmetic mean, which divides the sum of all prices by the number of products.
  • In contrast to RPI, the enormous population size is considered while computing CPI.
  • The cost of housing is not included in the CPI, including house depreciation, mortgage interest costs, building insurance, road fund license fees, council taxes, etc. On the other hand, RPI includes these charges in the total cost of the consumer products and services.
  • Charges, including stock broker fees, unit trust fees, university housing costs, and many more, are factored into the CPI. In contrast to RPI, which excludes such expenses.
  • Comparatively speaking, the CPI is less expensive than the RPI.
  • RPI includes housing expenditures such as house depreciation, road fund license, council tax, mortgage interest payments, etc., which is the main difference between the components. Such housing prices do not exist in the CPI, nevertheless.
  • The geometric mean is used by CPI to calculate price variance. RPI calculates the arithmetic mean by dividing the number of items by the total expenditures.
  • The national statistics agencies divide the consumption components into rural and urban consumers before calculating the CPI. Consumer Price Index alters the costs of household consumption of goods and services relative to a base year. The retail price fluctuations of the representative basket of goods and services are taken into account by the RPI, a measure of consumer inflation.
  • Regarding a base year, the consumer price index alters the costs of household consumption of goods and services. RPI, which tracks changes in the retail prices of a representative basket of items, is a measure of consumer inflation.


Both the CPI and the RPI track price changes, or the difference between what something cost last year and what it costs now. Since these two estimated price changes yet have distinct target audiences, this is the fundamental reason why the statistics of these two indices diverge. Additionally, certain commodities are covered by the CPI but not the RPI. The Retail Price Index (RPI), an earlier measure of inflation, is still released since it is needed to determine the cost of living and wage growth. Still, the government does not consider it an official inflation rate. Similarly, a number of items are taken into account when calculating RPI but not when determining CPI. Finally, the fact that they are calculated using various formulae further contributes to the differences between the two.

When compared to the average expenses from the base year, the CPI and RPI show changes in the cost of goods and services.RPI is calculated using arithmetic means, whereas CPI is calculated using the geometric mean. Additionally, RPI takes into account housing expenses like mortgage interest payments, but CPI does not. Since CPI is seen as a leading indicator of inflation, it is more pertinent than RPI.


  • https://eddisons.com/services/business-rates/what-is-the-difference-between-rpi-and-cpi-and-how-does-this-affect-business-rates/


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"Difference Between CPI and RPI." Diffzy.com, 2024. Fri. 19 Apr. 2024. <https://www.diffzy.com/article/difference-between-cpi-and-rpi-960>.

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