Read the base
Statistics Canada describes the Consumer Price Index as an indicator of changes in consumer prices and identifies a time base at which the index equals one hundred. An index value describes a relationship to that base, not the price tag of a representative product.
In an invented example, an index moving from one hundred to one hundred and twenty represents a twenty-percent increase from that base. Moving later from one hundred and twenty to one hundred and twenty-six is a five-percent increase, not six percent.
Distinguish change through time from comparison across places
A time index and an index designed to compare price levels between cities are different products. Statistics Canada’s inter-city methodology explicitly addresses cross-city price comparison. Two countries’ separate CPI values cannot be treated as a direct statement about which country has higher prices merely because one number is larger.
Check the basket, coverage, reference period and unit. If the programme rebases two series to the same starting value, that helps compare changes from the chosen date; it does not establish identical starting price levels.
A lower inflation rate also differs from falling prices. If an index continues to rise more slowly, its level can still be increasing.
Preserve the chart’s question
Record whether the story concerns the index level, the monthly change, the annual change or a cross-place comparison. Keep seasonal-adjustment labels and source dates where supplied. A clipped chart without its axis or base note may not support the conclusion in the accompanying social caption.
For a discussion, use the full indicator name and explain the reference point. Do not convert an index into a household budget or a particular product price without the relevant data. This article explains a statistical graphic and offers no financial recommendation. Its purpose is to keep an indexed change separate from a dollar amount, a price-level comparison and the rate at which prices are changing.
If a chart changes its base year, look for a comparable historical series from the source. Do not splice old and rebased index levels without the documented conversion.
Related questions
Is an index value a dollar price?
No. Read its unit and reference base.
Does slower inflation necessarily mean prices fell?
No. The rate can slow while the index level continues rising.
Sources and scope
Scope notes distinguish published documentation, supplied information and editorial methods. They do not report a hands-on service test.
- Statistics Canada: CPI metadata — Defines price-change indicator and time-base concept; no current index figure repeated.
- Statistics Canada: inter-city price methodology — Distinct cross-place price comparison product.
