OECD, the Organisation for Economic Co-operation and Development [http://www.oecd.org/]

Statistics Directorate - Purchasing Power Parities and Prices

Consumer price indices (CPIs) measure inflation as price changes of a representative basket of goods and services typically purchased by households. The G20 CPI aggregate reflects national CPIs for all G20 countries (with the exception of Turkey) that are not part of the European Union (EU) while it reflects the Harmonised Indices of Consumer Prices (HICP) for the EU, its Member States and for Turkey. It is an annual chain-linked Laspeyres-type index. The weights for each country in each link are based on the previous year’s relative share of individual final consumption expenditure of households and non-profit institutions serving households expressed in Purchasing Power Parities (PPPs).

The table presents the data for all non-EU countries. The HICP tables for France, Germany, Italy, the United Kingdom, and the euro area and European Union can be found under the HICP tables.

The G20 CPI has been calculated for the headline indicators only (CPI/ HICP All items).
Individual CPIs/HICPs All items of G20 economies refer to the COICOP classification (Classification of individual consumption by purpose) and national classifications usually adapted from COICOP classification. COICOP is only strictly applied by Korea and South Africa, while the COICOP/HICP classification (which is the COICOP classification adapted to the needs of the HICP) is used for the European Union and by Turkey. The other G20 economies use national classifications which in some countries, such as Australia and Japan are consistent with COICOP at the highest level. Table 7 in the Methodological Note Annex gives an overview of the systems of classification used and highlights the specific exclusions or inclusions by country.

Household sector

The published data is as follows:

• Index with 2010=100 as index reference year;
• Annual change: percentage change on the same period of the previous year (%);
• Previous period change: percentage change on the previous period (%).

Each published index or rate of change refers to the 'final monetary consumption expenditure' of the whole household sector of the corresponding geographical entity.

For CPI purposes, the definition of a household is essentially the same as in the System of National Accounts (SNA) 2008, which includes both private households, including those consisting of only one person, and institutional households such as religious orders, residential hospitals, prisons, etc. For many G20 economies, however, the institutional population and those living in non-private households are excluded from the scope of the CPI, often due to problems related to obtaining data on their consumption patterns. In these economies the indices are restricted to the private household population or a subset of the private household population. On the other hand, the HICP coverage of households includes institutional households.
Ideally, the CPI should be designed to be representative for households and not to a specific socio-economic group. However in some G20 economies such as Brazil, India and Indonesia, households with a low income level are excluded. Japan and Korea exclude households mainly engaged in agriculture, forestry and fishing, and all one-person households. Table 6 in the Methodological Note annex provides an overview of the socio-economic coverage.

The G20 consists of the following economies: Argentina*, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Korea, Mexico, the Russian Federation, Saudi Arabia, South Africa, Turkey, the United Kingdom, the United States, and the European Union. The G20 aggregate is calculated taking the fifteen individual country members of the G20 (other than France, Germany, Italy and the United Kingdom) plus the European Union as an aggregate.

* The data for Argentina are officially reported data. Data from January 2014 onwards are for a new national CPI (IPCNu) which differs substantively from the preceding CPI (the CPI for the Greater Buenos Aires Area, CPI-GBA). Because of the differences in geographical coverage, weights, sampling, and methodology, the IPCNu data cannot be directly compared to the earlier CPI-GBA data.As a consequence, the quarterly and annual inflation numbers for Argentina are excluded for Q1 2014 and 2014, respectively. Following a declaration of censure by the IMF on February 1, 2013, the public release of the IPCNu by end-March 2014 was one of the specified actions in the IMF Executive Board's December 2013 decision calling on Argentina to address the quality of its official CPI data. The IMF's Executive Board will review this issue again as per the calendar specified in December 2013 and in line with procedures set forth in the IMF's legal framework.

Regarding the G20 CPI aggregate, officially reported data for Argentina are included in the calculation of the aggregate G20 monthly inflation rate. As for the percentage change on the same period of the previous year and Index series (2010=100) data from January 2014 onwards exclude Argentina during 2014 for quarterly and annual inflation rates for Q1 2014 and 2014, respectively. These exclusions are due to problems of comparability of the pre-January 2014 CPI-GBA and the new IPCNu, as explained above. For the calculation of quarterly and annual inflation for the G20 aggregate, the implicit assumption is that the quarterly and annual inflation for Argentina in 2014 is the same as other G20 countries, on aggregate. Given Argentina's relatively small weight in the G20 index, OECD estimates are that each deviation in Argentina's CPI annual inflation of 10 percentage points from the G20 aggregate of remaining members, for example, will affect G20 aggregate inflation only by about 0.1 percentage points. Because Argentina is included in the G20 aggregate index series, there is an element of non-comparability in quarterly and annual inflation derived from that series for Q1 2014 and 2014, respectively. Users are cautioned, therefore, to use inflation estimates from the inflation tables rather than deriving inflation from the G20 aggregate index series.

The G20 CPI has been first released on the 14th October 2013. The time series starts from January 1996.

The G20 CPI reference year is 2010 = 100.

Following units are used:

• Index (unitless);
• Percentage change on the same period of the previous year (rates);
• Percentage change on the previous month (rates).

Month and quarter (indices and rates).

The G20 CPI is produced by the OECD Secretariat following a methodology agreed by the Inter-Agency Group on Economic and Financial Statistics. It is based on CPI/HICP data reported by G20 countries and Eurostat.

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The OECD will publish the CPI G20 aggregate each month as part of the OECD CPI News Release following the release of national CPI and HICP data by OECD and G20 economies (expected at the end of each month following the end of the reference period or the early beginning of the following month).

OECD website: http://www.oecd.org/std/prices-ppp/oecdconsumerprices-timetable.htm

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The G20 CPI is disseminated monthly.

The G20 CPI is disseminated as part of the OECD CPI Press Release of the current month.

Dissemintation through newsrelease and publication on database.

http://www.oecd.org/std/prices-ppp/oecdconsumerprices-timetable.htm

• Principal Global indicators website:
http://www.principalglobalindicators.org/default.aspx
• OECD.Stat Extracts:
http://stats.oecd.org/Index.aspx?DataSetCode=G20_PRICES

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For the more detailed Methodological Note, see the annex to the metadata file.

Methodological note agreed by the Inter-Agency Group on Economic and Financial Statistics (IAG).

When it comes to reliability, the primary goal of compiling and publishing G20 aggregates is the provision of indicators which sufficiently portray the reality of the overall economic development in the G20 area, in line with the principles of the quality frameworks subscribed by the international and supranational organisations constituting the IAG. This is necessary to ensure that G20 aggregates are fit for policy use and allow for a comparison with the average for the area under consideration as well as comparing developments across countries.

From these goals, it follows that the IAG would want to arrive at the best possible estimates for the G20 area, using internationally-comparable data from the countries constituting the relevant area.

The G20 CPI has been released within the framework of the Data Gaps Initiative and the Principal Global Indicators website. The PGI dataset provides internationally comparable data for the Group of 20 economies (G-20) and economies with systemically important financial sectors that are not members of the G-20. The PGI facilitates the monitoring of economic and financial developments for these jurisdictions.

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Some countries’ CPI data may not be available at the time of the release. India, for example, publishes its CPI on the last day of the month following the reporting period, and Saudi Arabia publishes its CPI with a time lag of two months in comparison to one month for other G20 economies. The current period CPI for countries whose CPI is unavailable will be imputed using the weighted average of the percentage CPI change of the previous period covering all the members whose CPI are available. Usually only the CPI data for Saudi Arabia are missing and the coverage is approximately 99.4 percent of G20 household consumption expenditure. The individual imputed values used for calculation of the G20 aggregate are not published.

The IMF has issued a declaration of censure and called on Argentina to adopt remedial measures to address the quality of the official CPI data. In the absence of a single validated alternative measure and given the small weight of Argentina in the G20 CPI, the official data of Argentina have been included in the G20 aggregate (each deviation in CPI inflation of 10 percentage points, for example, will affect G20 aggregate inflation by about 0.1 percentage point). Furthermore, in the absence of data for Saudi Arabia for the most recent period, the relevant CPI has been imputed using the weighted average of the percentage CPI change of the previous period covering all the members whose CPI are available. In the case of Australia, the values of the individual three months within a quarter have been set equal to the value of the available quarterly data.

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The OECD will publish the CPI G20 aggregate each month following the release of national CPI and HICP data by G20 economies and Eurostat (expected at the end of each month following the end of the reference period or the early beginning of the following month).

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In most instances, national CPIs are compiled in accordance with international statistical guidelines and recommendations. However, national practices may differ in the coverage and treatment of certain items and in the use of index number formulas. In particular, country methodologies for the treatment of owner-occupied housing vary significantly and, where included, carry large weights in the index. The European HICP is based on a harmonised approach and a single set of definitions in order to arrive at comparable measures of inflation in the EU; owner-occupied housing is excluded from the scope of the HICP. See methodological note annex for further information on comparability issues across G20 economies.

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Data used for the compilation of CPI All items for the G20 aggregate refer to HICPs for the European Union (including France, Germany, Italy, and the United Kingdom) as well as for Turkey, and to the national CPI for the other 14 countries. The preference for the use of the HICP, when available, rather than the national CPI is founded on the fact that Eurostat has developed a harmonised approach and a single set of definitions in order to arrive at comparable measures of inflation in the EU. Given the higher comparability of the HICPs, the use of HICPs when available is considered appropriate for the compilation of the CPI G20 aggregate.

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The G20 CPI is subject to revision as a result of revisions to the national accounts and the PPPs. In general, new weights for the most recent complete year are incorporated in either November or December of each year.
National CPI and HICP data of G20 economies are final at the date of the publication and are usually not revised. Still, HICP data, including back data, are revisable under the terms of an explicit revision policy.

National CPI and HICP data may be exceptionally revised when major changes in methodology or underlying structural data are implemented. In this respect, it can be noted that the weight reference periods of the national indices are subject to change – often referred to as a rebasing – every five years on average in G20 economies. National providers also typically use this rebasing to introduce methodological changes and/or a new basket of products, and these exceptionally lead to revisions of the respective CPI series (HICPs should not be revised when new baskets are introduced).

National CPIs for the G20 economies are mainly sourced from National Statistics Offices (NSOs), while HICPs for Turkey and the European Union are directly sourced from Eurostat, which in turn receives the data from the NSOs.

Monthly except for Australia (quarterly).

Data collection is carried out by the National Statistical Offices of the G20 member economies. For a complete list see Table 1 in the Methodological Note.

Data validation is carried out by the National Statistical Organisations of the G20 member economies. For a complete list see Table 1 in the Methodological Note.

The CPI All items for the G20 aggregate is calculated by aggregating the national CPI/HICP in each period using Household Final Consumption Expenditure (HFCE) and Final Consumption Expenditure of Non-Profits Institutions serving Households (NPISHs) as weights. The relevant country data are converted into a common currency (US dollars) using purchasing power parities (PPP) which are estimates of the rates of currency conversion that eliminate the differences in price levels between countries. The PPPs used in the zone estimates relate to HFCE specifically and are not the same as the PPPs for GDP, which are more commonly available.
The weights used to compile the G20 estimate are updated each year, usually in November or December. As a result of changes in the underlying national accounts data, the G20 estimate is subject to revision even though national CPIs/HICPs are rarely revised themselves. The main reason for updating the weights annually as opposed to aggregating with weights from a particular fixed base year is to allow for the changing importance of a country over time.

No seasonal adjustments are made.

For a more detailed description of the methodology, please see the annex.