sequence in June 2000, deCODE was busily scaling up its gene-hunting in dozens of diseases and publishing its first discoveries. The company used the most scalable DNA-reading technology of the time - microsatellite genotyping - to place and measure highly variable and therefore informative markers at hundreds of points along the genome. Analyzed in tandem with the genealogies, this made it possible to home in on regions of specific chromosomes that people with a given disease tended to have inherited from their common ancestors. Harbored within these regions, the thinking went, were genes or sequence variants associated with disease that could subsequently be found using finer-definition methods and tools. But the main significance of these early publications was the focus on analytics and the suggestive power of the approach. Much of the field and public attention was focused on the race between the publicly funded Human Genome Project (HGP) and the private company Celera to generate the complete sequence of a single whole genome to use as a reference for future research. This was a technical challenge to generate and assemble raw data. By contrast, deCODE was advancing a strategy for analyzing variation in tens of thousands of genomes through genetics, leveraging the nature of the genome as a means of replicating and transmitting information. The power of the genetics was on full view by 2002, when deCODE published a genetic map of the genome consisting of 5000 microsatellite markers, which the genealogies made it possible to order correctly across all the chromosomes. The map was critical to correcting and completing the public reference genome sequence in 2003, improving the accuracy of the HGP assembly from 93% to 99%. One key to this approach has been mass participation. From its early days, over 90% of people asked to participate in deCODE's disease research have agreed to do so. Participation is voluntary but not trivial. It requires going to a data collection center to have blood drawn, answer questionnaires, and undergo clinical examinations and tests relevant to a given disease. By 2003, more than 100,000 people had volunteered to take part in one or more of deCODE's three-dozen common diseases research programs. This number rose to 130,000 by 2007, and more than 160,000 by 2018. This represents two-thirds of all adult citizens. The genomes of some 60,000 of these participants had been directly sequenced by 2019, with thousands more being sequenced