|Unit||Index 2002=100, SA|
The Consumer Price Index (CPI) is an indicator of changes in consumer prices experienced by Canadians. It is obtained by comparing, over time, the cost of a fixed basket of goods and services purchased by consumers. Since the basket contains goods and services of unchanging or equivalent quantity and quality, the index reflects only pure price change.
Price movements of the goods and services represented in the CPI are weighted according to the relative importance of goods and services in the total expenditures of consumers. Each good or service is considered to be an element in a fictitious basket, and price movements are assigned a basket share or weight commensurate with the proportion of total consumption expenditure they account for. For example, Canadians as a whole spend a much larger share of their total expenditures on rent than on milk. As a result, a 10% price increase in rental rates will have a greater impact on the All-items CPI than a 10% increase in the price of milk. CPI basket shares have recently been updated at four year intervals; the data to specify them are obtained primarily from the Survey of Household Spending.
The above information was quoted from Statistics Canada where additional information can be found.
CPI inputs include the Suvery of Household Spending (SHS) and is adjusted annually to reflect the changes to household expenditures. This means that while CPI remains a consistent time series the basket of goods changes annual. For a summary of changes please see the SHS summary of change.
At this time, the source only reports seasonally adjusted CPI for the national geography. Moody's Analytics seasonally adjusts topline CPI figures for all available subnational geographies using the U.S. Census Bureau's X-12 ARIMA program.
The CPI common measure of core inflation is based on the CPI series adjusted to remove the effect of changes in indirect taxes and tracks common price changes across categories in the CPI basket.
The CPI median measure of core inflation is based on the CPI series and is treated to remove the effect of changes in indirect taxes and seasonally adjusted and corresponds to the price change located at the 50th percentileof the distribution of price changes in a given month..
The CPI trim measure of core inflation excludes CPI components whose rates of change in a given month are located in the tails of the distribution of price changes.
Revisions to non-seasonally adjusted series
The non-seasonally adjusted series of the CPI are never revised. From time to time, the base period of the CPI may be updated. The official time base was changed from 1992=100 to 2002=100 starting with the CPI for May 2007. The change is strictly an arithmetic conversion, which alters the index levels, but leaves the percentage changes between any two periods intact, except for differences in rounding.
Revisions to seasonally adjusted series
The seasonally adjusted indexes are the only CPI series open to revisions. Each month, the previous month's seasonally adjusted index is subject to revision. The seasonally adjusted values for the last three years are revised with every January data release.
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