. Identification re ention and reduction o state essness age, gender, ethnicity, and diversity of participants.58 Results of participatory assessments will, in particular, inform States, international organizations and partners about the causes of statelessness; obstacles to the acquisition of nationality; the protection needs of stateless populations, including status and documentation; and the population’s own capacity to contribute to a solution.59 If a national census is being planned, this opportunity can be used to promote the inclusion of specific questions in the census questionnaires that permit the identification of possible stateless persons and to obtain socio-economic data about them.60 In June 2015, the United Nations Economic Commission for Europe (UNECE) endorsed the Conference of European Statisticians’ Recommendations for the 2020 Censuses of Population and Housing, which highlighted the need to identify stateless persons.61 A common challenge when measuring statelessness through a population census is that persons may identify themselves as stateless even though they have a nationality, or they may think they have citizenship when, in fact, they do not. However, responses to questions on nationality in a census may indicate statelessness concerns that can and should be further analysed and cross-checked. Census-takers should, therefore, be made aware of potential statelessness issues and trained accordingly. UNHCR and other UN agencies can assist relevant authorities in formulating questions for census questionnaires as well as coding for responses and parameters for data analysis.62 Population profiling, including targeted surveys are also important tools for identification and planning purposes. Where a governmental policy framework and adequate procedures exist, a survey may be combined with registration, information, and legal advice to assist individual stateless persons in accessing relevant procedures for the acquisition of citizenship, documentation procedures or, in the absence of solutions, a determination procedure that is linked to a secure status. A survey is particularly suited to situations in which the target population is relatively concentrated and located in a geographically-limited area.63 OSCE participating States have increasingly turned to ODIHR for technical advice and support in modernizing their population registers, especially in response to recommendations on voter registration made by 45