Årindex

Årindex, or year index, is a statistical measure that summarizes how a variable changes over a calendar year or over a one-year period. It is used to compare performance across years, to adjust for scale, and to present growth or inflation in a compact form. In practice, an årindex is built by selecting a base year and setting its value to a reference level, often 100. The values for subsequent years express the relative level of the variable compared with the base year. Common formulations include: year-over-year index, where index_t = (value_t / value_{t-1}) × 100, showing percentage change from the previous year; and an annual index based on yearly averages, where the annual figure is derived from monthly data and then set relative to the base.

Interpretation: An index value above the base indicates growth or higher levels, while a value below indicates decline. For example, an årindex of 110 means a 10% increase since the base year.

Applications: used in economics and statistics to track inflation (price indices), production or employment levels, GDP, and other financial indicators. In Sweden and other Nordic countries, annual indices are often used in official statistics, wage negotiations, and policy analysis.

Limitations: results depend on the choice of base year and methodology; they smooth short-term fluctuations and may obscure seasonal patterns or structural breaks. Data quality and revisions can affect comparability over time.