    tion, many countries in the region maintain high barriers to naturalization. This means that some migrants may remain permanent immigrants without any access to citizenship in their host country. They may even lose their citizenship in their country of origin due to their long absence, but never obtain citizenship in their new country of residence. The acquisition of nationality by historical migratory but long-term resident populations is frequently a thorny political issue in numerous countries across Asia. Japan, for instance, has one of the lowest naturalization rates among OECD countries.77 In several countries in Asia, naturalization is often a cumbersome and fraught process.78 Even fewer countries in the region have legal provisions that offer facilitated naturalization to stateless persons.79 1.5 Statelessness in Asia: Context and Causes As discussed above, Asia is a major epicentre of the statelessness phenomenon. Of the 4.4 million stateless persons reported globally, the majority are located in the Asia-Pacific region, most notably in Bangladesh, Myanmar, and Thailand.80 The scope of statelessness in the region, as well as globally, is likely far more extensive, as estimating the number of stateless persons in the region is a fraught exercise, due to the lack of reliable data and statistics. The UNHCR’s annually estimated numbers of stateless populations rely mostly on government statistics, which themselves may be incomplete. Furthermore, many countries in Asia report no figures at all. The widespread lack of mechanisms to determine statelessness further contributes to a dearth of data.81 Accordingly, the UNHCR figures should be taken as a conservative estimate, with the true figure likely being much higher. But what is evident from the available data is that Asia is home to the largest number 77 Vonk (n 72) 17–21. See also Choo Chin Low, ‘The Historical Development of the Nature of ‘Desirability’ in Naturalisation Regimes in East and Southeast Asia’ (2021) 25(4) Citizenship Studies 491. 79 Vonk (n 72) 26. 80 UNHCR, ‘2022 Asia and the Pacific Regional Trends Report’ (n 12) 6. 81 The Philippines are a notable exception, as discussed in Francis Tom Temprosa’s chapter, ‘Persuading to Ratify: A Calculus of the Ratification of the Statelessness Convention in Asia’. 78 https://doi.org/10.1017/9781009399555.003 Published online by Cambridge University Press