every month. A second and unique pillar of deCODE's work is the genealogies. Geneticist Mary Claire King, whose family-based research in the early 1990s led to the discovery of the BRCA1 and BRCA2 breast cancer genes, predicted not long after deCODE's founding that the ability "to trace the genealogy of an entire nation...could become one of the treasures of modern medicine." In 1997, deCODE formed a partnership with local software firm Fridrik Skulason ehf to accelerate the creation of a comprehensive, computerized national genealogy database. It drew on all available sources, from the earliest calfskin records and sagas through the 1703 census and parish records to the contemporary national registry. By the early 2000s they had created what is still today the most comprehensive genealogy of an entire country. It links together all living citizens through virtually complete records back to 1703 (itself recognized by UNESCO as the world's first nominal national census) and stretches back to before the settlement of the country in the ninth century. In the research version of the database, the identities of individuals are encrypted via the same anonymization system used for DNA and medical data, so that the data can be correlated. And In 2003, deCODE launched a public-facing, online version of the database, called Íslendingabók, or the Book of Icelanders. Anyone with an Icelandic social security number could request a password and then research their family tree and see their nearest family connection to anyone else in the country. Within its first month online, more than one-third of the population had requested a password. By 2020, it had over 200,000 registered users and more than 900,000 linked entries, comprising the majority of Icelanders who have ever lived. On an average day, nearly 6000 people, or close to two percent of all citizens, consult the database. In a country that is essentially a huge extended family with a correspondingly keen interest in how its members are related, Islendingabok has become a constant in national life and a daily and direct means of social engagement with deCODE's work. But in scientific terms, the ability to understand the precise genealogical relationships of all participants in its research projects has given deCODE an abiding advantage as a discovery enterprise, ensuring that its genomic and medical datasets have remained among the largest and best powered collections anywhere. At each successive advance in technology for reading DNA the genealogies