Appendix 2 - Analytical series

1 Each review of the Consumer Price Index, the ABS assesses the analytical requirements of its users and the current relevance of each special analytical series published. The following separate inflation series are currently published to assist users analyse the CPI: 

• All groups CPI, seasonally adjusted
• Underlying trend series -  'Trimmed mean' and 'Weighted median'
• International trade exposure series - Tradables component original and seasonally adjusted.
• International trade exposure series - Non-tradables component; original and seasonally adjusted.
• All groups CPI - goods component; original and seasonally adjusted.
• All groups CPI - services component; original and seasonally adjusted.
• Market goods and services excluding various volatile items
• All groups CPI excluding various items.
• Discretionary and Non-Discretionary.
• Discretionary excluding tobacco.

2 These analytical series are published in table 6 of Consumer Price Index, Australia and are compiled by taking subsets of the CPI basket. Each series and their composition are outlined below.

3 The ABS has classified expenditure classes as goods or services based on the majority of products in each category. In the CPI, 60 out of the 87 expenditure classes, accounting for approximately 53 per cent of the All groups CPI by weight, have been classified as goods. The remaining 27 expenditure classes, accounting for approximately 47 per cent of the All groups CPI by weight, have been classified as services.

4 The CPI Tradables and Non-tradables series, collectively known as the International Trade Exposure series, measure the contribution of imported and domestic inflation to overall household inflation. Identifying the source of household inflation aides the understanding and forecasting of inflation; as well as supporting monetary and fiscal policy decisions.

5 The International Trade Exposure series classifies the CPI expenditure classes as either tradables or non-tradables by assessing the degree to which their prices are affected by domestic developments and international competition. The tradables and non-tradables series are available each month in table 8 of Consumer Price Index, Australia.

6 Expenditure classes were defined as tradables firstly by assessing the level of imports and exports to Australian production. If exports or imports exceeded 10 per cent of Australian production, the expenditure class was classified, by default, as tradable. To determine the final classification, supplementary data were used to assess the appropriateness of each of the expenditure classes default classification. Following this, the contribution of domestic taxes and subsides to the price paid by consumers was analysed. Since taxes and subsidies are a domestic impact on inflation, these expenditure classes were classified as non-tradables where these make a large contribution to the price paid by consumers.

7 For further information see the feature article Review of the Consumer Price Index International Trade Exposure Series.

8 The ABS released the tradables and non-tradables price indexes from the June quarter 1998 based on 1993-1994 and 1994-1995 Input-Output tables and related product correspondences. For the 15th series CPI, the tradable and non-tradable classification was based on the 2001-02 Input-Output data and related product correspondences. For the 16th series CPI, the 2006-07 Input-Output tables and related product correspondences were used and an optimal threshold of 10% was applied to determine whether an industry is exportable or importable . The 2013-14 Input-Output tables were used to update the classification in December quarter 2016.

9 More information is available in Australian National Accounts: Input-Output Tables.

10 Table A2.1 shows which expenditure classes are classified as tradables and which are classified as non-tradables. In aggregate, 49 expenditure classes, which account for approximately 35 per cent of the CPI by weight, are classified as tradables. The remaining 38 expenditure classes, accounting for approximately 65 per cent of the CPI by weight, are classified as non-tradable.

11 Seasonal adjustment helps the analysis of price movements as it estimates and then removes influences that are systematic and calendar related from a time series. The seasonal adjustment methodology used to produce analytical measures of underlying inflation was replaced with standard ABS seasonal adjustment methodology with the introduction of the 16th series CPI. This ensures that seasonally adjusted CPI data are consistent with other ABS data and results in more transparent and robust analytical series. Seasonal adjustment factors are calculated using the history of price changes up to the current month CPI, and are revised each month. 

12 The following analytical series are published using the ABS seasonal adjustment methodology:

(i) All Groups CPI, seasonally adjusted: The time series begins at April 2024, which is the index reference period (April 2024 = 100.00).

(ii) Group and subgroup level price indexes (seasonally adjusted): comprises the seasonally adjusted groups and subgroups at the weighted average of eight capital cities level. These time series begin at different months, depending on the earliest month that monthly data is available for all expenditure classes contributing to the group or subgroup. The earliest starting month of the group and subgroup series is September 2017.

(iii) Expenditure class level price indexes (seasonally adjusted): produced for all expenditure classes for which seasonality has been identified at the weighted average of eight capital cities level. Standard seasonal adjustment methods cannot be applied to series with fewer than three years of data.  The September 2025 seasonally adjusted index value is equal to 100 (the September 2025 seasonal factor), and this value will be revised each month due to revisions to the seasonal factor. 

(iv) Trimmed mean and Weighted median: two measures of underlying inflation. In the 15th series, these measures were calculated using a seasonal adjustment methodology developed by the Reserve Bank of Australia (RBA)¹. The 16th series replaced this methodology with standard ABS seasonal adjustment methodology. These time series begin at April 2024, which is the index reference period. 

(v) Tradables and Non-tradables (seasonally adjusted): these series measure the contribution of imported and domestic inflation to overall household inflation at the weighted average of eight capital cities level. These time series begin at April 2024, which is the index reference period.

13 More information on the seasonal adjustment methodology is available in Information paper: Seasonal adjustment of Consumer Price Indexes, with updates found in Seasonal adjustment for the new complete Monthly Consumer Price Index (CPI).

14 Market items are those available on the open market. The volatile items are Fruit, Vegetables and Automotive fuel.