What linked registries are making it possible to know about whole populations

The strongest evidence on the site comes disproportionately from a few countries, and the reason is data: the Nordic countries and the Netherlands can join births, deaths, diagnoses, prescriptions, education and income for every resident through a personal identifier, so a question about a whole population can be answered rather than sampled. That capability is spreading unevenly. England has built linkages across hospital, primary care and death data that were impossible a decade ago, though access is slow and fragmented; Scotland and Wales have gone further with dedicated data environments; Korea's national insurance database and Japan's are opening to research; the United States still cannot link nationally and works through claims data and cohorts instead. The stream of new sources, linkages and access arrangements is what the site's data-watch entries record; the driver's question is what they change — which findings became possible, which were overturned when a whole population replaced a sample, and where the gaps in linkage still determine what can be known.

Status

building

Direction

strengthening

Would change our view

A country without a national identifier achieving population-scale linkage by another route; or evidence that linked-data findings systematically differ from cohort findings on the same questions.

Trackers

Gaps

Access rules and timeliness compared across countries; what is linked in Japan, Korea and Germany specifically; the effect of data-protection law on what can be studied.