The primary means of recruitment for deCODE research has been through collaboration with physicians across the health service who construct lists of patients with different diseases who are then invited to take part. Participation entails not only written informed consent but also filling out health questionnaires; undergoing detailed clinical examination and measurements; and giving blood for the isolation of DNA; all of this takes place at a special clinic and requires the commitment by participants of several hours to complete. The IHD was never built, its scientific and business rationale largely superseded by the response of Icelanders to contribute their data one by one. By 2003, with some 95% of people asked to participate agreeing to do so, more than 100,000 were taking part in the study of one or more of three-dozen diseases. By 2007, this had grown to 130,000; and by 2018 to more than 160,000. This is roughly 70% of all adult citizens, 60,000 of whom have had their whole genomes sequenced.