The price of food and non-alcoholic beverages rose by 0.4% in October, according to Statistics Iceland, and by 3.9% in the previous twelve months. At the same time, stores have cut or frozen prices, and many goods are indeed cheaper. Many observers find this paradoxical, to say the least. If grocery stores are cutting prices, shouldn’t the food component of the CPI fall as well? Answering this requires, first of all, that we examine how the component is calculated.
How are food prices calculated?
The CPI measures what it costs to buy the same basket of goods and services from month to month. Statistics Iceland (SI) staff collect prices over a period of roughly one week each month, and the collection covers more than 20,000 prices of about 4,000 goods and services items. The food basket is part of this operation, and the price collection process involves monthly measurements of goods in predefined categories, although it is not disclosed precisely what goods are measured.
Each product is assigned a weight, depending on how large a share of household expenditure it represents. The weights are based on SI’s expenditure study, and the database for the study is revised once a year. Food and non-alcoholic beverages currently account for 15.3% of the index and are the third-largest category, after housing and transportation, as can be seen in the chart below. Within the food item, dairy products, grains, and meat weigh heavily, while other categories carry far less weight.

