Methodology & Sources

1. Editorial policy

Immigration Factbook is an independent database presenting the effects of immigration across 20 Western countries, based primarily on official sources, with clearly labelled academic or institutional sources where no official primary estimate exists. We receive no funding from any political party, foundation, lobby group, or government.

Data is sourced primarily from primary official publications (statistics offices, treasuries, central banks, international organisations). Where primary data is unavailable or requires synthesis, we use peer-reviewed academic work or institutional research (e.g. Pew Research, National Academies), clearly identified with source type, funder, and methodological limits. Newspapers are not used as data sources.

2. Source hierarchy

3. Definitions

Definition of "immigrant"

We follow each country's official definition. The default is "foreign-born", but some countries (France, Belgium, etc.) use "foreign national" as their primary statistical category. The definition used is stated on each country page.

"Immigrant background"

Refers to persons with at least one foreign-born parent. Used primarily in Scandinavian official statistics.

Fiscal cost methodology

Net fiscal impact estimates vary significantly by country (static vs dynamic analysis, scope of federal/local/national levels, included benefit items, etc.). We report each country's estimate using the methodology applied by its official institution, and do not directly compare figures across countries with different methodologies.

Employment gap

Difference in percentage points between the employment rate of immigrants and that of the native-born population. These are unadjusted raw figures that do not control for age, sex, or educational composition. Source: latest published data from each national statistics office.

PISA gap

Difference in maths scores between students with an immigrant background and native-born students (PISA 2022). "After ESCS correction" means the socio-economic, cultural, and social status index (ESCS) has been statistically removed. Source: OECD PISA 2022 Volume I.

Per-capita crime rates

Suspect counts or conviction counts divided by each group's population (rate as %). We use per-capita rates rather than absolute counts because groups of very different sizes cannot be meaningfully compared in absolute terms. Source: official data from national police agencies and justice ministries.

4. Limits of international comparison

• Definitions of "immigrant" differ across countries — direct numerical comparisons require caution.
• Fiscal cost estimates vary greatly by methodology; multiple estimates may exist for the same country.
• Crime statistics are unadjusted raw figures that do not control for age, sex, urban concentration, or socioeconomic status — they do not isolate the effect of immigrant background per se.
• PISA gaps may reflect differences in school systems and the composition of each country's sample.
• Where data are unavailable, we write "—" or "no official data published".

5. Update process

Figures on each page are updated in line with each national statistics office's annual publication schedule. The date of last update is noted in each page's metadata. Updates are made manually, after direct verification of the primary source, before publication.

Until new data become available, we use the most recent published figures and clearly state the reference year. Unverified data are not published.

6. About this site

Immigration Factbook is an independent database providing official immigration statistics for Western countries in Japanese and English. Launched in 2025. Its aim is to improve access to this category of information for Japanese-speaking readers, for whom very little primary-source material has previously been available.

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