# Concepts and definitions

- Annual change
Annual change is the relative change of the index in comparison with the corresponding time period one year ago (e.g. annual change of total index of consumer prices, i.e. inflation).

- Base index
In the base index the price of the calculation period is always compared with the base period. In the base index weights are usually changed less often than yearly, for example, at intervals of five years.

- Chain index
In the chain index the comparison takes place always between successive calculation periods. In the chain index the change in two calculation periods is used to take forward the index point figure of the desired base period. In the chain index the weights are changed in principle in each calculation period.

At times the chain index is also mentioned in such cases where the comparison period is retained fixed in comparisons within the year, but the comparison period and the weight structure of the index is changed whenever the year changes.

- Consumer price
The real price paid by consumers for a good or service (including taxes, in retail trade).

- Consumer price statistics
A monthly release made on the Consumer Price index material, which contains average prices for certain daily consumer goods and some other simple commodities by major region.

- Effect list of price changes
The list that shows the changes of commodities and/or aggregate level indices and the effects of the changes on the total index. The review periods are changes from the previous month, from the previous year's December and from the previous year to the review period. Available from the official Consumer Price Index monthly.

- Index
An index is a ratio describing the relative change in a variable (e.g. price, volume or value) compared to a certain base period (e.g. one year). The index point figure for each point in time tells what percentage the given examined variable is of its respective value or volume at the base point in time. The mean of the index point figures for the base period is 100.

- Index formula
Index formula is a mathematical function by means of which an individual key figure describing change is calculated from observation values (e.g. Fischer, Laspeyres and Paasche index formulas).

- Monthly change
Monthly change is the relative change in the index from a time period one month earlier. The change is usually expressed as a percentage.

- Point figure
Point figure is a change quantity used in price indices, which expresses the price, average price or index of the comparison period relative to the price, average price or index of the base period. The point figure of the base period is usually denoted by the number hundred. For example, if the point figure for a commodity at a certain point in time is 105.3, it means that the price of that commodity has risen by 5.3 per cent from the base period.

- Special index
A "tailored" index made to customer order, where the commodities and weight structure are defined by the customer. The weights used in the index can be either Statistics Finland's or the customer's own weights.

- Total index
Total index is the index calculated as a weighted average from all the sub-series belonging to the description area of the index. Total index can be calculated as a weighted index of detailed price index series describing different commodity groups.

- Weight structure
Describes what meaning each sub-index (commodity, employee group, etc.) belonging to the index has for total index.

Official Statistics of Finland (OSF):
Consumer price index [e-publication].

ISSN=1799-0254. Helsinki: Statistics Finland [referred: 18.3.2018].

Access method: http://www.stat.fi/til/khi/kas_en.html

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