Meijers Committee standing committee of experts on international immigration, refugee and criminal law 65% of those naturalised are dual nationals after naturalisation; 20% automatically loses their previous nationality and 15% actually renounces their previous nationality.16 Numbers Data on the number of dual nationals are available for a few countries only. Registration policies vary considerably. In the Netherlands, the registration of dual nationality in the population register was abolished in 2014 because such registration could give rise to discrimination.17 Of course, the non-registration did not change the legal status of the dual nationals and it is now known that at least the tax authorities continued to illegally register and use information on dual nationality (see paragraph 1). In Germany, registration was introduced in 2015. The previous non-registration obscured among others the dual nationality of hundreds of thousands ethnic Germans (Aussiedler) who migrated from Poland, Romania, Russia and Kazakhstan.18 The number of dual national Dutch in the Netherlands in 2014 was 1.3 million, i.e. 8% of the total population.19 Their number doubled since 1998. The German Statistical Office in 2015 estimated the total number of German nationals with another nationality living in Germany to be in between 1.7 million and 4.3 million. According to the Office the first number, based on self-reporting in a micro-census, is probably too low and the second number based on the population registration is probably too high.20 In 2010, the number of French citizens with dual nationality was estimated, on the basis of census data, at 3.3 million, i.e. 5% of the total population.21 In the 2011 census in England and Wales 0.6 million residents reported to have two passports.22 The actual number of UK nationals with dual nationality most probably is far higher. Predominantly of immigrant origin In Germany and the Netherlands, about half of the dual nationals acquire dual nationality at birth and the other half later in life.23 Considering the four main causes of dual nationality 16 G.-R. de Groot & M. Vink (2008), Meervoudige nationaliteit in Europees perspectief. Een landenvergelijkend overzicht, Universiteit Maastricht, p. 118 and Monitor naturalisatie en optie 2014-2017, The Hague, Ministerie van Justitie en Veiligheid, 2018, p. 48-49. 17 H.U. Jessurun d‘Oliveira, ‘Vreemde nationaliteit en de Basisregistratie Personen Hoe lang nog schoorvoeten?’, Asiel & Migrantenrecht 2016, p. 480-483. 18 Thränhardt 2017. 19 Centraal Bureau voor de Statistiek (CBS), Nederlanders; geslacht, dubbele nationaliteit, 1 januari 1998 – 2014, https://opendata.cbs.nl/statline/#/CBS/nl/dataset/70798ned/table?ts=1602360016541. 20 Statistisches Bundesamt, Bevölkerung und Erwerbstätigkeit: Bevölkerung mit Migrationshintergrund: Mikrozensus 2015, Fachserie 1, Reihe 2.2., Wiesbaden, p. 17 and Thränhardt 2017, p. 18-20. 21 P. Simon (2010), Trajectoires et Origines, Enquête sur la diversité des populations en France, Paris: INED/INSEE, p. 117-122 and Le Monde 24 December 2015. 22 https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationestimates/adho cs/006277ct06442011censusdualpasportukandirishnationaltocountry. 23 Statistisches Bundesamt 2015, CBS 2014. 4