The Statistics Act specifies that the disseminating agencies cannot publish, or otherwise make available to any individual or organization, statistics that would enable the identification of data for any individual person or entity without prior consent.
The Statistics Act (Chapter 317) designates the Chief Statistician as the national statistical co-ordinator, responsible for developing national statistical standards and standardizing definitions, classifications, terms, procedures and concepts for use in statistical activities; and for promoting the observance of approved national statistical standards.
The methodology used in the compilation of PPIs in Singapore makes reference to international recommendations given in the “Producer Price Index Manual 2004” by the International Monetary Fund (IMF).
Definition: The Producer Price Index, known as Domestic Supply Price Index (DSPI), measures the change in the price level of goods manufactured locally and imports which are retained for use in the domestic economy.
Industrial coverage: Importers and local manufacturers are surveyed.
Product coverage: The DSPI covers the supply of goods in Singapore whether from external or local sources. The external supply component ("retained imports") refers to imports less re-exports. The local supply component is total sales of producers less the portion they export. The index covers 489 imported commodity items and 213 domestically-manufactured commodity items.
Exceptions to coverage: Goods for military use, aircraft, shipbuilding/ship repair and precious stones are excluded because it is difficult to obtain suitable price quotations.
Data sources: The data used to derive the DSPI are obtained from the Monthly Survey of CIF Prices of Imported Goods and the Monthly Survey of Ex-factory Prices for Locally Manufactured Products. The data on retained imports and domestic sales are derived from the external trade statistics provided by the International Enterprise Singapore and from the Census of Manufacturing Activities provided by the Economic Development Board.
Sources of weights: The weight for each commodity item in the DSPI is equal to its share in 2011 total domestic supply, as derived from external trade statistics and the Census of Manufacturing Activities. The weight for each commodity item in the DSPI is proportional to the value of its total supply or availability in the domestic market in 2011. The sources of supply are both external and local. The external supply component is the value of retained imports (that is, the value of imports less re-exports). The local supply component is the domestic sales value (that is, the value of total sales of manufacturers, less the value of the portion they exported).
Period of current index weights: 2011.
Frequency of weight updates: Every 5 to 6 years.
The index is re-based and the weights are revised every 5 to 6 years to ensure that the 'basket' of commodities remain representative of changing domestic supply pattern.
Establishment selection: The top ten importers and manufacturers of each product group are shortlisted for the initial selection of establishments.
Product/transaction selection: Purposive sampling is used. Product selection is based on the following factors:
Regular and frequent imports/sales.
Continuity of price data over a period of time.
Substantial volume of transactions.
Descriptions should be specific and sufficiently detailed for pricing.
Product/transaction specification: Products with detailed description pertaining to brand, grade, size, type of packaging and distinguishing features are specified.
Sample sizes: 1,285 importers and 593 manufacturers provide monthly price quotations of 489 imported commodity items and 213 domestically manufactured commodity items.
Price collection methods: Price data are collected by mail/fax/e-mail questionnaire and supplemented by telephone queries as appropriate.
Aggregation structure: DSPI is aggregated by the Standard International Trade Classification, Revision 4.1 (SITC, Rev 4.1) Sections, Divisions, Groups and Items.
Treatment of missing prices: For missing prices, estimates are made on the basis of trends for similar products. At the same time, respondents will be queried to authenticate such missing information. When a product is permanently unavailable, a replacement is selected either from the same respondent or from an alternative establishment.
Selection of replacement items: Replacement items should have similar characteristics as those originally selected in the item structure.
Adjustments for quality differences: Prices are adjusted to remove the effect of quality changes wherever possible.
Introducing new products: New products are only introduced when a weight updating exercise is initiated.
Seasonal items: Seasonal items are not common and are excluded.
Verification of procedures: All price quotations are inspected before compilation. Abnormal price quotations are identified for follow-up actions to be initiated. Such actions may include querying affected respondents and seeking expert opinions.
The quarterly Economic Survey of Singapore (QES) publishes: (1) quarterly and annual data for the latest year on: (a) the DSPI at 1-digit level of SITC, and (b) the year-on-year percentage change in the DSPI at 1-digit level of SITC; and (2) quarterly time series data for the latest 9 quarters and annual time series data for the latest 4 years on DSPI; and year-on-year percentage changes.
The annual Economic Survey of Singapore (AES) publishes annual time series for DSPI and percentage change at 1-digit level of SITC as follows: (1) annual data for the latest 4 years; and (2) quarterly data for the latest 8 quarters.
The Yearbook of Statistics publishes annual time series on DSPI at 1- and 2-digit levels of SITC for the latest seven years.
The DSPI is subjected to revision after original publication. Data may be revised to include late submissions and amendments by respondents. Details of the rebasing of DSPI to reference year 2012 are published in an Information Paper entitled "The Rebasing of Singapore Manufactured Products and Domestic Supply Prices Indices (Base Year 2012=100)".
Data are disseminated on the Domestic Supply Price Index (DSPI), a ‘modified Laspeyres’ index (2012=100), where the weight reference year 2011 preceded the price reference year 2012. The index measures price changes of locally manufactured goods and imports which are retained for use in the domestic economy.
An information paper on the Rebasing of Singapore Manufactured Products and Domestic Supply Price Indices (Base Year 2012=100) is available on the DOS website. This paper is available free of charge.A technical notice is also appended to the monthly report "Singapore Manufactured Products and Domestic Supply Price Indices".
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