The Danish government does not collect data on citizens' religion so the exact number of Muslims in Denmark is not known with certainty.[29] The Danish researcher Brian Jacobsen, who makes regular estimations based on the national origin of immigrants and their descendants, estimates that by October 2017 Muslims made up 306.000 persons or 5.3% of the Danish population.[2] Over 70% of Muslims in Denmark are Danish citizens,[2] and the majority are first- or second-generation immigrants.[30] In 2013, roughly 2,000 to 5,000 Danish Muslims were converts to the religion.[31] Muslims are unevenly distributed around Denmark with the majority concentrated in major cities.[32] Approximately 47.4% of Danish Muslims live in Greater Copenhagen, 9.4% in Aarhus, and 5.5% in Odense.[33]