« Consumer Price Index (CPI) » : différence entre les versions

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  | cours = [[Introduction à la macroéconomie]]
  | cours = [[Introduction to Macroeconomics]]
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*[[Federica Sbergami|Sbergami, Federica]]<ref>[https://www.unige.ch/gsem/en/research/faculty/all/federica-sbergami/ Page personnelle de Federica Sbergami sur le site de l'Université de Genève]</ref><ref>[https://www.unine.ch/irene/home/equipe/federica_sbergami.html Page personnelle de Federica Sbergami sur le site de l'Université de Neuchâtel]</ref><ref>[https://www.researchgate.net/scientific-contributions/14836393_Federica_Sbergami Page personnelle de Federica Sbergami sur Research Gate]</ref>
*[[Federica Sbergami|Sbergami, Federica]]<ref>[https://www.unige.ch/gsem/en/research/faculty/all/federica-sbergami/ Page personnelle de Federica Sbergami sur le site de l'Université de Genève]</ref><ref>[https://www.unine.ch/irene/home/equipe/federica_sbergami.html Page personnelle de Federica Sbergami sur le site de l'Université de Neuchâtel]</ref><ref>[https://www.researchgate.net/scientific-contributions/14836393_Federica_Sbergami Page personnelle de Federica Sbergami sur Research Gate]</ref>
*[[Nicolas Maystre]]<ref>Researchgate.net - [https://www.researchgate.net/profile/Nicolas_Maystre Nicolas Maystre]</ref><ref>Google Scholar - [https://scholar.google.com/citations?user=B73U0wsAAAAJ&hl=en Nicolas Maystre]</ref><ref>VOX, CEPR Policy Portal - [https://voxeu.org/users/nicolasmaystre0 Nicolas Maystre]</ref><ref>[http://nicolas.maystre.ch/ Nicolas Maystre's webpage]</ref><ref>Cairn.ingo - [https://www.cairn.info/publications-de-Nicolas-Maystre--104530.htm Nicolas Maystre]</ref><ref>Linkedin - [https://www.linkedin.com/in/nicolas-maystre-82660737/?originalSubdomain=ch Nicolas Maystre]</ref><ref>Academia.edu - [https://unctad.academia.edu/NicolasMaystre Nicolas Maystre]</ref>
*[[Nicolas Maystre]]<ref>Researchgate.net - [https://www.researchgate.net/profile/Nicolas_Maystre Nicolas Maystre]</ref><ref>Google Scholar - [https://scholar.google.com/citations?user=B73U0wsAAAAJ&hl=en Nicolas Maystre]</ref><ref>VOX, CEPR Policy Portal - [https://voxeu.org/users/nicolasmaystre0 Nicolas Maystre]</ref><ref>[http://nicolas.maystre.ch/ Nicolas Maystre's webpage]</ref><ref>Cairn.info - [https://www.cairn.info/publications-de-Nicolas-Maystre--104530.htm Nicolas Maystre]</ref><ref>Linkedin - [https://www.linkedin.com/in/nicolas-maystre-82660737/?originalSubdomain=ch Nicolas Maystre]</ref><ref>Academia.edu - [https://unctad.academia.edu/NicolasMaystre Nicolas Maystre]</ref>
  | enregistrement =  
  | enregistrement =  
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*[[Aspects introductifs de la macroéconomie]]
*[[Introductory aspects of macroeconomics]]
*[[Le Produit Intérieur Brut (PIB)]]
*[[Gross Domestic Product (GDP)]]
*[[L'indice des prix à la consommation (IPC)]]
*[[Consumer Price Index (CPI)]]
*[[Production et croissance économique]]
*[[Production and economic growth]]
*[[Chômage]]
*[[Unemployment]]
*[[Marché financier]]
*[[Financial Market]]
*[[Le système monétaire]]
*[[The monetary system]]
*[[Croissance monétaire et inflation]]
*[[Monetary growth and inflation]]
*[[La macroéconomie ouverte : concepts de base]]
*[[Open Macroeconomics: Basic Concepts]]
*[[La macroéconomie ouverte: le taux de change]]
*[[Open Macroeconomics: the Exchange Rate]]
*[[Equilibre en économie ouverte]]
*[[Equilibrium in an open economy]]
*[[L'approche keynésienne et le modèle IS-LM]]
*[[The Keynesian approach and the IS-LM model]]
*[[Demande et offre agrégée]]
*[[Aggregate demand and supply]]
*[[L'impact des politiques monétaires et fiscales]]
*[[The impact of monetary and fiscal policies]]
*[[Trade-off entre inflation et chômage]]
*[[Trade-off between inflation and unemployment]]
*[[La réaction à la crise financière de 2008 et la coopération internationale]]
*[[Response to the 2008 Financial Crisis and International Cooperation]]
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{{Translations
{{Translations
| fr = L'indice des prix à la consommation (IPC)
| fr = L'indice des prix à la consommation (IPC)
| es =  
| es = Índice de precios al consumidor (IPC)
}}
}}


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== Inflation correction ==
== Inflation correction ==


To be able to compare the purchasing power of a certain income in different years, the (nominal) value of this income must be corrected by the evolution of the cost of living. Ex: <math>salary_{2004}^{2000} = salary^{2000} \times \frac {CPI_{2004}}{CPI_{2000}} = \text{purchase power of salary 2000 in 2004}</math>.
To be able to compare the purchasing power of a certain income in different years, the (nominal) value of this income must be corrected by the evolution of the cost of living. Ex: <math>salary_{2004}^{2000} = salary^{2000} \times \frac {CPI_{2004}} ; {CPI_{2000}} = \text{purchase power of salary 2000 in 2004}</math>.


Example 1 :
Example 1 :
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James has a real salary almost 4 times higher than Jordan's in his first year of the NBA.
James has a real salary almost 4 times higher than Jordan's in his first year of the NBA.


== L'année de base ==
== The base year ==
Les indices de prix sont généralement fixés arbitrairement à 100 pour une période de référence : attention aux comparaisons !
Price indices are generally set arbitrarily at 100 for a reference period: beware of comparisons!


Si un indice vaut 174 et un autre 130, il faut avoir la même année de base (ou année indice ou « année 100 ») pour savoir lequel a évolué le plus rapidement.
If one index is 174 and another is 130, it is necessary to have the same base year (or index year or "year 100") in order to know which one has moved the fastest.


Exemple :  
For example:  
:<math>IPC 1995 = 102.6</math> et <math>IPC 1997 = 103.9</math> (1993 = 100)
:<math>IPC 1995 = 102.6</math> and <math>IPC 1997 = 103.9</math> (1993 = 100)
taux d’inflation (entre 1995 et 1997) = <math>\frac {103.9 - 102.6}{102.6} = 0.01267 = 1.267%</math>
Inflation rate (between 1995 and 1997) = <math>\frac {103.9 - 102.6}{102.6} = 0.01267 = 1.267%</math>
Ou plus simplement, par approximation :
Or more simply, by approximation:
:taux d’inflation (entre 1995 et 1997) = <math>103.9 - 102.6 = 1.3%</math>
:Inflation rate (between 1995 and 1997) = <math> 103.9 - 102.6 = 1.3%</math>
(approximation valable uniquement pour des petites variations, i.e. < 10 %)
(approximation valid only for small variations, i.e. < 10%)


== Inflation et déflation ==
== Inflation and deflation ==
[[Fichier:Intromacro inflation et déflation 1.png|400px|vignette|centré]]
[[Fichier:Intromacro inflation et déflation 1.png|400px|vignette|centré]]


Il est possible de constater que l'inflation est faible entre janvier 2010 et décembre 2009 et qu'il y a de la déflation entre janvier 2009 et janvier 2010.
It can be seen that inflation is low between January 2010 and December 2009 and that there is deflation between January 2009 and January 2010.


== Importance de mesurer correctement l’IPC ==
== Importance of measuring the CPI correctly ==
L'IPC est utilisé continuellement dans la vie politique et économique des pays et les autorités de politique économique ainsi que les individus se basent sur l'observation de l'ICP pour prendre leur décisions.
The CPI is used continuously in the political and economic life of countries and economic policy authorities as well as individuals rely on the observation of the CPI to make their decisions.


En « révisant » l’IPC a la baisse (cf. les biais qu’on a vu plus tôt), le gouvernement peut montrer une augmentation du salaire réel plus importante que l’augmentation effective et justifier les politiques économiques existantes. La politique monétaire adoptée par la Banque Centrale est choisie, entre outre, sur la base de l'évolution de l'IPC.
By "revising" the CPI downwards (see the biases we saw earlier), the government can show a larger increase in real wages than the actual increase and justify existing economic policies. The monetary policy adopted by the Central Bank is chosen, among other things, on the basis of the evolution of the CPI.


L’IPC est utilisé pour indexer certains contrats, comme les retraites, les salaires, la régulation des prix de l’électricité, etc.
The CPI is used to index certain contracts, such as pensions, wages, electricity price regulation, etc. The CPI is also used for the indexation of certain contracts.


Pour évaluer la rentabilité d’un investissement il nous faut une mesure de l’évolution du coût de la vie :
To evaluate the profitability of an investment we need a measure of the evolution of the cost of living:
:Taux d’intérêt réel = taux d’intérêt nominal – taux d’inflation
:Real interest rate = nominal interest rate - inflation rate.


== Taux d’intérêt nominal et réel ==
== Nominal and real interest rates ==
[[Fichier:Intromacro Taux d’intérêt nominal et réel 1.png|400px|vignette|centré]]
[[Fichier:Intromacro Taux d’intérêt nominal et réel 1.png|400px|vignette|centré]]


= Résumé =
= Summary =


L’IPC montre le coût d’un panier de bien et services dans une année donnée par rapport au coût du même panier dans une année de base. Le changement en pourcentage de l’IPC nous donne le taux d’inflation.
The CPI shows the cost of a basket of goods and services in a given year compared to the cost of the same basket in a base year. The percentage change in the CPI gives us the rate of inflation.


L’IPC est une mesure imparfaite du cout de la vie pour quatre raisons :
The CPI is an imperfect measure of the cost of living for four reasons:
*biais de substitution ;
*substitution bias;
*l’importance de nouveaux biens ;
*the importance of new goods;
*les changements pas mesurable de la qualité des biens ;
*unmeasurable changes in the quality of goods;
*hétérogénéité des paniers de consommation des différents individus.
*heterogeneity in the consumption baskets of different individuals.


Le déflateur du PIB diffère du IPC sur deux aspects :
The GDP deflator differs from the CPI in two respects:
*L’IPC se concentre sur un panier de consommation type et le déflateur sur les biens produits dans l’économie ;
*The CPI focuses on a standard consumption basket and the deflator focuses on the goods produced in the economy;
*L’IPC utilise un panier fixe de biens et services alors que le déflateur du PIB ajuste la composition du panier de façon à refléter la structure de production chaque année.
*The CPI uses a fixed basket of goods and services while the GDP deflator adjusts the composition of the basket to reflect the structure of production each year.


Des variables monétaires mesurées dans différents moments dans le temps doivent être ajustées par leur pouvoir d’achat (IPC) afin d’être comparées. Pour pouvoir dire quelque chose sur l’évolution du pouvoir d’achat des individus dans le temps il faut mesurer correctement l’IPC.
Monetary variables measured at different points in time must be adjusted by their purchasing power (CPI) in order to be compared. In order to say something about the evolution of individuals' purchasing power over time, the CPI must be measured correctly.


L’IPC est utilisé pour fixer des salaires, des retraites, le prix de certain bien sous régulation publique.
The CPI is used to set wages, pensions, the price of certain goods under public regulation.


Le taux d’intérêt réel est ce qui détermine la décision d’investir et il est donné par le taux d’intérêt nominal moins le taux d’inflation.
The real interest rate is what determines the decision to invest and is given by the nominal interest rate minus the inflation rate.


= Annexes =
= Annexes =

Version actuelle datée du 1 avril 2020 à 11:37


In this chapter we focus on how to measure the cost of living, and its evolution. This will be useful to compare the purchasing power of different incomes at different points in time. For example, a salary of 200 can buy more than a salary of 2000 if the cost of living in the first case is more than 10 times lower than in the second case.

The consumer price index allows us to measure changes in the cost of living. It is a measure of the evolution of the general price level faced by the consumer, and therefore of inflation, i.e. the percentage change in the price level from one period to the next).

Languages

Construction and CPI issues[modifier | modifier le wikicode]

Definition and construction of the CPI[modifier | modifier le wikicode]

The CPI is the measure of the cost of the basket of goods and services purchased by the 'typical consumer'. It tells us the evolution of its cost of living. If the CPI increases, the typical consumer will have to spend more money to consume the same basket of goods and services, and therefore his cost of living will have increased.

Construction of the CPI and the inflation rate :

  1. the basket of the typical consumer is defined and fixed by conducting consumption surveys to determine the weight given to each good in the total expenditure ;
  2. price surveys are conducted at regular intervals;
  3. the value of the basket is calculated at different points in time based on the prices collected;
  4. a base year is chosen and the value of the index is calculated in each year by taking the ratio of the cost of the basket to the base year and multiplying it by 100;
  5. the percentage inflation rate is given by the annual change in the CPI: .

Construction of the CPI: example[modifier | modifier le wikicode]

1. We define the basket of goods purchased by a typical consumer:

Dépense d’un consommateur représentatif par catégorie de bien (pour nous: hamburgers et hot-dogs).

2. We do price surveys every year:

Construction de l’IPC 2.png

3. The cost of the (fixed) basket is calculated each year :

Construction de l’IPC 3.png

4. A base year is chosen for the index and the CPI is calculated:

Construction de l’IPC 4.png

5. The CPI is used to calculate the annual inflation rate :

Construction de l’IPC 5.png

Development of the Swiss CPI[modifier | modifier le wikicode]

Évolution ipc en suisse 1.png

Problems with the CPI[modifier | modifier le wikicode]

The CPI is not a perfect measure of the cost of living. There are several reasons for this:

  • substitution bias: price changes will affect the composition of the typical consumer's basket. The index overestimates the increase in the cost of living by not taking into account the ability of consumers to substitute goods.
  • introduction of new goods: this gives more choice to consumers who can substitute the consumption of certain goods with new goods, thus reducing their cost of living (downloading films from the internet is not part of the CPI, but the cinema ticket is). The increase in the cost of living is again overestimated.
  • Improved quality of goods: for the same price, the consumer can buy goods that give him greater satisfaction or that perform better. The CPI overestimates the increase in the cost of living by ignoring quality.
  • It is not a "true" cost-of-living index: it does not take into account health insurance premiums, taxes, social security contributions, etc. It is not a "real" cost-of-living index. It does not take into account health insurance premiums, taxes, social security contributions, etc. (only consumer goods and services are considered).
  • Heterogeneity of consumption baskets: young versus old, poor versus rich, etc. The average consumption basket does not really exist → limits of the average basket if the composition of society changes or the prices of the goods consumed by each group do not evolve in the same way → comparisons between difficult people (and even more so between countries!).

CPI versus GDP deflator[modifier | modifier le wikicode]

The GDP deflator was given by : GDP deflator =

Differences from the CPI

  1. The CPI focuses on the price evolution of goods consumed in the economy, while the GDP deflator focuses on the price evolution of goods produced in the domestic economy: the price of imported goods is included in the former but not in the latter.
  2. The CPI compares the evolution of the cost of a basket of goods that is fixed, while the GDP deflator looks at the evolution of the price of commonly produced goods in relation to the price of goods produced the previous year. (Paasche index versus Laspeyres index)

Indice de Paasche et Laspeyres[modifier | modifier le wikicode]

The GDP deflator is a "Paasche index":

GDP deflator =

in the case of hot dogs and hamburgers =

The consumer price index is a "'Laspeyres index'":

in the case of hot dogs and hamburgers =

CPI versus GDP deflator[modifier | modifier le wikicode]

IPC versus déflateur du PIB 1.png

Two other alternative measures of price changes are the Producer Price Index (PPI), which measures changes in the cost of a (fixed) basket of goods and services purchased by producers (this is used to predict changes in the CPI), and the Import Price Index (IPI).

Changes in the main price indices since 1990[modifier | modifier le wikicode]

Évolution des principaux indices de prix depuis 1990 1.png

Correction of macroeconomic variables for inflation[modifier | modifier le wikicode]

Inflation correction[modifier | modifier le wikicode]

To be able to compare the purchasing power of a certain income in different years, the (nominal) value of this income must be corrected by the evolution of the cost of living. Ex: .

Example 1 :

  • George Washington's income in 1789 was USD 25,000.
  • George Bush's income in 2007 was USD 450'000.
  • The consumer price index with base 100 in 1789 is 2000 in 2007.

Which of the two George's has a higher real income (higher purchasing power)? .

Eexample 2 :

  • LeBron James' salary in 2003 (his first year in the NBA) is $4 million.
  • Michael Jordan's salary in 1984 (his first year in the NBA) is $550,000.
  • CPI in 2003 with base 100 in 1984 is $200.

James has a real salary almost 4 times higher than Jordan's in his first year of the NBA.

The base year[modifier | modifier le wikicode]

Price indices are generally set arbitrarily at 100 for a reference period: beware of comparisons!

If one index is 174 and another is 130, it is necessary to have the same base year (or index year or "year 100") in order to know which one has moved the fastest.

For example:

and (1993 = 100)

Inflation rate (between 1995 and 1997) = Or more simply, by approximation:

Inflation rate (between 1995 and 1997) =

(approximation valid only for small variations, i.e. < 10%)

Inflation and deflation[modifier | modifier le wikicode]

Intromacro inflation et déflation 1.png

It can be seen that inflation is low between January 2010 and December 2009 and that there is deflation between January 2009 and January 2010.

Importance of measuring the CPI correctly[modifier | modifier le wikicode]

The CPI is used continuously in the political and economic life of countries and economic policy authorities as well as individuals rely on the observation of the CPI to make their decisions.

By "revising" the CPI downwards (see the biases we saw earlier), the government can show a larger increase in real wages than the actual increase and justify existing economic policies. The monetary policy adopted by the Central Bank is chosen, among other things, on the basis of the evolution of the CPI.

The CPI is used to index certain contracts, such as pensions, wages, electricity price regulation, etc. The CPI is also used for the indexation of certain contracts.

To evaluate the profitability of an investment we need a measure of the evolution of the cost of living:

Real interest rate = nominal interest rate - inflation rate.

Nominal and real interest rates[modifier | modifier le wikicode]

Intromacro Taux d’intérêt nominal et réel 1.png

Summary[modifier | modifier le wikicode]

The CPI shows the cost of a basket of goods and services in a given year compared to the cost of the same basket in a base year. The percentage change in the CPI gives us the rate of inflation.

The CPI is an imperfect measure of the cost of living for four reasons:

  • substitution bias;
  • the importance of new goods;
  • unmeasurable changes in the quality of goods;
  • heterogeneity in the consumption baskets of different individuals.

The GDP deflator differs from the CPI in two respects:

  • The CPI focuses on a standard consumption basket and the deflator focuses on the goods produced in the economy;
  • The CPI uses a fixed basket of goods and services while the GDP deflator adjusts the composition of the basket to reflect the structure of production each year.

Monetary variables measured at different points in time must be adjusted by their purchasing power (CPI) in order to be compared. In order to say something about the evolution of individuals' purchasing power over time, the CPI must be measured correctly.

The CPI is used to set wages, pensions, the price of certain goods under public regulation.

The real interest rate is what determines the decision to invest and is given by the nominal interest rate minus the inflation rate.

Annexes[modifier | modifier le wikicode]

References[modifier | modifier le wikicode]