Data & Methodology

How prices are converted

Each local price is converted to euro using the ECB reference rate for the day it was observed, then normalized to 100 grams.

eur_price     = local_price × ecb_rate(currency, observed_at)
eur_per_100g  = eur_price ÷ package_weight_g × 100

The rate used is stored on every observation, so any conversion can be reproduced from the local price.

Which observations count

An observation contributes to a current value only when all of these hold:

• it is not flagged for review;
• it was observed within the last 48 months;
• its package weight is greater than zero;
• its price is greater than zero;
• it has an observation date.

Freshness policy

Each country is classified by the age of its most recent observation:

• Up to 18 months: up to date, fully eligible for the current ranking.
• 18 to 48 months: still ranked, but marked as out of date.
• Over 48 months: moved to the historical archive and excluded from current claims.

Which statistic is used

The statistic follows the number of observations. We do not compute values the sample cannot support.

• 1 observation: the observation itself is shown, never an average.
• 2 to 10 observations: arithmetic mean, presented as preliminary.
• 10 or more observations: median as the headline value, with the mean shown beside it.

All values are rounded to the cent. Displayed precision does not imply that the estimate is precise.

Confidence levels

Levels are derived from the rules below, never assigned by hand:

• Preliminary: 1 or 2 observations, or observations from a single source.
• Developing: 3 to 9 observations from more than one source.
• Established: 10 or more observations from more than one source.
• Out of date: Marked out of date when the most recent observation is older than 18 months. It does not indicate an error — only that a newer reading is needed.

Where store, retailer and city are all unknown — which is the case for every observation collected before the extended contribution form — we count distinct observation dates as a proxy for independence, and the interface states which of the two it is counting.

The three ranking views

The ranking is split into three separate views, selectable from the filters:

• Current ranking: Only countries with enough evidence to support a national estimate.
• Preliminary observations: Countries with few observations: real data, but not a robust ranking.
• Historical archive: Observations older than 48 months, excluded from current claims.

Duplicates

Observation counts are a public confidence signal, so duplicates are blocked rather than counted.

• A submission is rejected when an observation already exists with the same country, date, package size, price, currency and store. The check runs both at submission time and again before publication.
• Near-duplicates are flagged for manual review and do not contribute to any value until resolved.

Countries and territories

The ranking lists entities that have their own ISO code and their own retail prices. They are classified as:

• Sovereign state: a widely recognized state.
• Dependency: has an administering state, shown next to the name.
• Territory: a distinct ISO entity with no single agreed administering state.

The classification is statistical, not political: it describes how data is grouped, not the status of a territory.

Version history

v1.1 — The observation city counts towards source independence alongside store and retailer. Only classic Nutella enters the public figures. · v1.0 — First versioned methodology: eligibility rules, freshness policy, statistic selection, confidence levels, duplicate rules and geographic classification.