2.3.7

Use of Index Numbers

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Index Numbers

Index numbers are used by economists to both represent and to understand economic data in a much clearer way. Economists typically report price levels in each period as an index number, rather than a dollar amount.

Index numbers

Index numbers

  • Economists create price indices to calculate an overall average change in relative prices over time.
    • E.g. if you were told the average price of housing in the US was $256,010, and it is forecast to rise to $268,221, it is hard to process this data. But if you were told the index level was forecast to rise from 107 to 110, you would have a better idea of the significance of this change.
How to calculate an index number

How to calculate an index number

  • You need to choose a "base". This is commonly a year but doesn't have to be.
  • It is the “thing” that everything else is being compared to.
    • E.g. if the base year is 2008, then the index number in 2009 is being compared to 2008, the chosen base year.
  • It is convention to set the base year index number equal to 100.
  • To calculate an inflation rate we use the following formula: (New value / Base year value ) x 100.
Example of calculating an index number

Example of calculating an index number

  • In this example, 2015 has been chosen as the base year, with an index value of 100.0.
  • To calculate the index value in 2016, the calculation is ($257,111 / $250,010) x 100 = 102.8.
  • This represents a 2.8% rate of inflation between 2015 and 2016. This is calculated by finding the percentage change in the index number over that period.
Jump to other topics
1

Microeconomics

1.1

Competitive Markets: Demand & Suply

1.1.1Markets & Demand1.1.2Diminishing Marginal Returns1.1.3Supply1.1.4Market Equilibrium1.1.5Price Mechanism1.1.6Consumer & Producer Surplus1.1.7IB Multiple Choice - Demand1.1.8IB Multiple Choice - Supply
1.2

Elasticity

1.2.1Elasticities of Demand1.2.2Factors Affecting Price Elasticity of Demand1.2.3Elasticity of Supply1.2.4Price Elasticity of Supply1.2.5IB Multiple Choice - Price Elasticity of Demand1.2.6IB Multiple Choice - Price Elasticity of Supply1.2.7IB Multiple Choice - Other Elasticities
1.3

Government Intervention

1.3.1Indirect Taxes & Subsidies1.3.2Application Question - Taxing Prices or Quantities1.3.3Subsidies & Price Controls1.3.4Deadweight Loss & Government Intervention1.3.5Elasticity & Tax Incidence1.3.6IB Multiple Choice - Government Intervention
1.4

Market Failure

1.4.1Types of Market Failure1.4.2Introduction to Externalities1.4.3Negative Externalities1.4.4Policy for Negative Externalities1.4.5Positive Externalities1.4.6The Deadweight Welfare Loss of Externalities1.4.7Case Study - The Externalities of Education1.4.8Public Goods & the Free-Rider Problem1.4.9Asymmetric Information1.4.10End of Topic Test - Market Failure1.4.11Application Questions - Market Failure
1.5

HL: Theory of the Firm & Market Structures

1.5.1Theory of the Firm & Market Structures
2

Macroeconomics

2.1

The Level of Overall Economic Activity

2.1.1The Circular Flow of Income2.1.2Defining GDP2.1.3Limitations of GDP2.1.4IB Multiple Choice - Economic Indicators2.1.5Business Cycles2.1.6Output Gaps
2.2

Aggregate Demand & Aggregate Supply

2.2.1The Aggregate Demand Curve2.2.2Components of Aggregate Demand2.2.3Shape of the Aggregate Demand Curve2.2.4Shifts in Aggregate Demand2.2.5IB Multiple Choice - Aggregate Demand2.2.6Short & Long-Run Aggregate Supply2.2.7Alternative Models of LRAS2.2.8Equilibrium in the AD-AS Model2.2.9Output Gaps & the AD-AS Model
2.3

Macroeconomic Objectives

2.3.1Introduction to Unemployment2.3.2Limitations of Unemployment2.3.3Types of Unemployment2.3.4Causes & Impact of Unemployment2.3.5Defining Inflation2.3.6Measuring Inflation2.3.7Use of Index Numbers2.3.8The Consumer Price Index2.3.9Consequences of Inflation2.3.10Causes of Inflation2.3.11Inflation & Unemployment Tradeoff2.3.12The Short-Run Phillips Curve2.3.13The Long-Run Phillips Curve
2.4

Economic Growth, Poverty & Inequality

2.4.1Measuring Economic Growth2.4.2Determinants of Productivity2.4.3Economic Growth & Productivity2.4.4Absolute & Relative Poverty2.4.5Inequality2.4.6Inequality 22.4.7Lorenz Curve2.4.8Government Policy on Poverty2.4.9End of Topic Test - Poverty & Inequality2.4.10Application - Inequality & Poverty
2.5

Fiscal Policy

2.5.1Introduction to Fiscal Policy2.5.2Fiscal Policy and AD-AS Model2.5.3Fiscal Policy Lags2.5.4Automatic Stabilizers2.5.5IB Multiple Choice - Fiscal Policy
2.6

Monetary Policy

2.6.1Objectives of Monetary Policy2.6.2Monetary Policy Implementation2.6.3Monetary Policy & AD-AS Model2.6.4Monetary Policy Lags & Pitfalls
2.7

Supply-Side Policies

2.7.1Supply-Side Policies2.7.2Supply-Side Policies 2
3

The Global Economy

3.1

International Trade

3.1.1Globalisation3.1.2Globalisation for LEDCs3.1.3Globalisation for MEDCs3.1.4Comparative Advantage & Trade3.1.5Protectionism3.1.6Arguments for Protectionism3.1.7Arguments Against Protectionism3.1.8End of Topic Test - Globalisation & Trade3.1.9Case Study - Globalisation & Trade
3.2

Exchange Rates

3.2.1Floating Exchange Rates3.2.2Fixed Exchange Rate3.2.3Effect of a Stronger & Weaker Dollar
3.3

The Balance of Payments

3.3.1Balance of Payments3.3.2Balance of Payments 23.3.3FDI & Reducing a BoP Deficit
3.4

Economic Integration

3.4.1Customs Unions & WTO3.4.2Merged Currency
3.5

Terms of Trade

3.5.1Absolute & Comparative Advantage3.5.2Gains from Trade3.5.3Terms of Trade3.5.4IB Multiple Choice - Comparative Advantage & Trade
3.6

Economic Development

3.6.1Factors Influencing Growth & Development3.6.2International Institutions3.6.3Measures of Development3.6.4Barriers to Development3.6.5Case Study - The Bottom Billion3.6.6End of Topic Test - Emerging & Developing
3.7

The Role of Domestic & International Factors

3.7.1Interventionist Strategies3.7.2Development Strategies3.7.3Development Promotion Policies3.7.4End of Topic Test - Growth & Global Development3.7.5Application Questions -Growth & Global Development
3.8

The Role of International Trade

3.8.1International Institutions3.8.2End of Topic Test - Globalisation & Trade
3.9

The Role of Foreign Aid

3.9.1Aid3.9.2Limitations of Aid3.9.3Support for Aid3.9.4Application Questions - Developing Countries

Practice questions on Use of Index Numbers

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    If the price level increases from an index of 140 to 154, what does this indicate?Multiple choice
  2. 2
    If the base year data (where the index = 100) for a firm's revenue is $200 000, what is the index number for revenue equalling $600 000?Multiple choice
  3. 3
    What is the index number which represents a doubling in value compared to the base year?Multiple choice
  4. 4
    How to calculate an index number:Fill in the list
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Measuring Inflation

The Consumer Price Index