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Norway has given its dead a national ID, revealing patterns that were previously hidden
For the first time, researchers can follow individual lives across generations.
For more than 200 years, Norwegians have left traces in church records, censuses, and archives.
These historical sources are now being brought together in a historical population register. It can also be linked to all data collected by public and private entitites about individuals.
For the first time, researchers can follow individual lives across generations. In this way, they can uncover patterns in migration, family relationships, and health that were previously hidden.
A historical population register
Norway’s National Population Register is among the most detailed in the world. Thanks to unique personal identification numbers, the country has maintained an accurate overview of its population since 1964.
The Historical Population Register (NHPR) is built on the same principle, but extends back in time. NHPR includes everyone who has lived in Norway since 1801. It therefore expands knowledge of the population from around 60 years in the current register to 225 years.
In the register, each individual is assigned a unique identifier, like today’s personal identification numbers. This makes it possible to recognise the same person across different historical sources. The same applies to people who until now have been difficult to trace in historical sources.
This enables new ways of documenting and tracing individuals over time.
“We hope these unique IDs will be used when referring to historical persons from the general population. This will provide better documentation and verifiability than is possible today,” says Lars Holden.
He is the project leader and research director at the Norwegian Computing Center.
The NHPR consists of both an open and a restricted part. The open part is accessible to everyone via histreg.no, while the restricted part includes more recent data and is only available to approved research projects.
How life courses are linked
To trace life courses, the register brings together information on births, names, places of residence, migration, and deaths.
The data comes from censuses, church records, emigration lists, and a range of thematic registers. Examples include the war sailor register, a register of politicians from 1814, and records of public employees.
Linking across sources is carried out both automatically and manually. A large part of the work is carried out by volunteer genealogists and local historians. They help improve and expand the data. This makes the NHPR one of Norway’s largest citizen science projects.
These connections provide a more comprehensive picture of individuals and events.
“Seeing the data in context can provide entirely new insight into why something happened,” says Holden.
When life courses are analysed at the individual level, the register can also offer new perspectives on broader historical developments. In some cases, these linkages can document events in the lives of well-known individuals and provide new context to established historical narratives.
“For example, the NHPR shows that Einar Gerhardsen was arrested in the 1920s. Such information helps us better understand the labour movement in the interwar period,” says Holden.
Linking past and present
A key feature of the infrastructure is that historical data can be linked with information from more recent times.
The NHPR demonstrates how privacy can be safeguarded, even when many sources are combined and parts of the work are carried out through open volunteer efforts. Researchers can gain access to data for up to seven generations linked to a wide range of today’s population data.
Access is strictly regulated. The data is adapted so that individuals cannot be identified. Access is only granted to approved research projects.
This makes it possible to study developments over longer periods of time. For example, a researcher can examine relationships between family conditions, living standards, and health.
New avenues for research
When data is linked at the individual level, patterns that were previously difficult to detect become visible.
One of the clearest examples is migration. While emigration to America has long dominated historical narratives, data from the NHPR shows that domestic migration was, in some periods, just as extensive as previously assumed.
Another finding concerns women’s migration.
It has often been assumed that women mainly moved with their families, typically in connection with their husband's work. However, data shows that migration among women increased significantly towards 1920. Many single women moved to the cities to work in sectors such as education, healthcare, and trade.
The register also opens new possibilities for source criticism. When the same individual can be traced across multiple sources, it becomes clear that the information doesn’t always align.
Analyses of birth dates in the 1910 and 1920 censuses show that errors occur more frequently than previously assumed. The discrepancies follow patterns related to age, geography, and social background.
Such variations are not necessarily a problem. They can also provide insight into how historical data was recorded and how reliable it is.
A valuable resource for researchers
“The NHPR is a gift to researchers and archive users. For the first time, it’s possible to access comprehensive overviews of personal data across archival sources and over several centuries,” says Anette Clausen. She is head of department at the National Archives of Norway.
Researchers who are already using the register also highlight new opportunities.
June Haugrud is a sociologist and researcher at the European University Institute, where she studies sibling relationships and migration.
“It's unique to have a population register with such extensive coverage while also being able to analyse family relationships. In other contexts, this would simply not be possible. For my research, it means I can study demographic developments, such as migration decisions, while taking family relationships into account,” she says.
An infrastructure for the future
Holden believes the register will have a long lifespan and remain relevant far into the future.
“This could become one of the longest-lasting research infrastructures. It will be just as relevant in 200 years as it is today,” he says.
Few other infrastructures can be used across so many disciplines while also providing insight into both individual lives and broader societal developments.
The work is now being expanded through a Nordic collaboration, making it possible to trace historical lives across national borders.
Historically, demographic research has largely been limited to national datasets. Linking data across countries opens up new opportunities to study migration, societal development, and health in a broader context.
The aim is to share knowledge, methods, and infrastructure. It will also provide new insights into demographic changes, public health, and family formation in the Nordic region.
The Norwegian Historical Population Register is therefore not only a technical solution, but a new starting point for understanding how society has developed – through lives that can be traced, compared, and put into context.
Reference:
Holden et al. Historisk befolkningsregister som et autoritetsregister for personer og verktøy for lokalhistorisk forskning (Norwegian Historical Population Register as an authority register for persons and a tool for local historical research), Heimen, 2025. DOI: 10.18261/heimen.62.4.4
Holden et al. Norwegian Historical Population Register, 1801-present, Historical Life Course Studies, 2026. DOI: 10.52024/hlcs25461
