Groceries cost … more today than a year ago.

From the Consumer Price Index (CPI) published by INE, the same index used to measure official inflation. Every month INE collects the prices of the same products in shops across Spain and calculates an index for each type of product (the 'headings'): bread, eggs, oil… bolsillo downloads those indices back to 2002 from INE's public API and updates them automatically when a new figure comes out, in the middle of each month.

By comparing the index for two months. If the egg index was 80 a year ago and is 90 today, eggs have gone up 12.5% (90 ÷ 80 − 1). What today's shop cost in each year is worked out the same way: your amount times that December's index, divided by today's index. These aren't prices in a shop, but how much prices change on average.

That what cost €1 now costs €1.10. If it falls 10%, it costs €0.90. Percentages don't add up: two years in a row at 10% make 21%, not 20%.

CPI is an average for all of Spain, across many shops, brands and pack sizes. Your shop depends on what you buy and where: if you eat lots of fruit or eggs, it will feel pricier than average; if you buy own-brand or at another chain, it may come out cheaper.

Energy, fertiliser, animal feed and transport became more expensive after Russia's invasion of Ukraine, and drought cut harvests such as olive oil. In 2023 and 2024 VAT on basic foods was cut, which held prices back a little until VAT returned to its usual level.

CPI's food group: everything you eat, from meat to bread. It doesn't include alcoholic drinks or cleaning products, which are listed separately.