# 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.

- 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).

- 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.

- Price index of public expenditure
The price indices of public expenditure (PIPE) measure the development of prices in the expenditure of central and local governments. The indices have been used for decision-making about central and local government finances, and for diverse studies. The indices are suitable for calculations at constant prices, and for estimations of volume changes in the public economy and expenditure.

- Quarterly change
Quarterly change refers to the relative change in the index of the quarter compared with the index of the previous quarter. The change is usually expressed in percentages.

- 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):
Price index of public expenditure [e-publication].

Helsinki: Statistics Finland [referred: 20.1.2020].

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