UNHCR STATISTICS TECHNICAL SERIES: 2019/1 number of stateless persons for countries with unspecified methodological bases are difficult to evaluate regarding their historical usage, estimation methods, reporting gaps, and inconsistent reporting intervals. UNHCR’s country-level data on stateless populations is disaggregated demographically by sex and age, however the availability of disaggregated data varies from country to country. Specification of ethnic and other population characteristics is sometimes available in the population descriptions, particularly when estimation techniques target narrowly-defined populations such as specific ethnic groups that are known to be stateless. Furthermore, stateless populations are estimated according to different definitions such as de jure statelessness (cited as “stateless” in the database), de facto stateless populations (“de facto stateless”) and populations of unknown nationality (“undetermined”). Depending on methodological choices, enumerated groups can include combinations of the aforementioned categories. Although the distinction between what constitutes de facto, de jure and undetermined nationality is not always clear due to methodological uncertainties and contradictions across databases, de facto and de jure stateless populations are never reported simultaneously within the same country, however for some countries they are both reported across different years. Data Sources The PopStats database contains data for 82 countries that have reported figures to UNHCR from 2009 to 2018. Six countries that reported figures during this timeframe have data which is poorly documented or consists of oneoff reporting for a single year only. Among them are countries that have stopped reporting but previously cited fewer than five stateless persons for one year and similar cases with low numbers, short reporting timeframes, and limited methodological information. As UNHCR works to improve gaps with governments and other partners, Global Trends 2018 included 78 countries reporting on statelessness, an increase from 75 in 2017. Of these estimates, 55 derive from government data, 13 from UNHCR-assisted initiatives, 3 from NGOs, and 7 unspecified. The methods used to collect data for these figures include 41 registration procedures, 9 government censuses, 4 surveys, 14 other estimation techniques, and 10 unspecified methods. These figures include 21 de jure stateless populations, 18 de facto stateless populations, 17 undetermined populations, 12 combinations of de facto stateless and undetermined populations, and 10 combinations of de jure stateless and undetermined populations. UNHCR In 2018, UNHCR itself was involved in the reporting of 13 of 78 countries for which stateless figures were available. While this assistance spanned countries in Africa, Asia, Europe, and Latin America and the Caribbean, efforts were concentrated in the successor states of the former Soviet Union and the former Yugoslavia. In 2018, UNHCRreported figures without supplementary government reporting included two estimates; four registration exercises; and two unspecified figures. Combined reporting conducted together with governments include UNHCR registration in an additional two countries; estimates in an additional one; and two surveys. Associated methodological bases include six registrations, three estimates, two surveys, and two unspecified bases. These figures typically correspond to undetermined populations: UNHCR sources cited six undetermined populations, one de jure 3 UNHCR / October, 2019