Our research has revealed the pressing need to reach a consensus on definitions. Although such concepts as institutions11, disability12, gender identity or ethnicity can be contested, international human rights law provides some guidance in this matter. In accordance with General Comment No. 9 of the CRC-Committee, the definitions should be broad enough to cover all children who, due to their unique characteristics, may benefit from special protection and the programmes developed for them.13 Achieving better data comparability facilitates not only comparative research but, most importantly, identification and implementation of promising practices. At the same time, States should not limit themselves to establishing an appropriate definition in law, but to ensure that it is understood and interpreted uniformly by the personnel responsible for collecting data. For instance, as some studies have revealed, the limitations in data collection may be related to the lack of adequate training of child welfare workers in identifying children with disabilities.14 2.2 Data Disaggregation Due to the limited data collection capacities as well as lack of awareness, children are usually represented as a homogenous group and States rarely provide disaggregation by other features than age and sex. At the same time, during the research phase some groups were found to be particularly vulnerable, e.g. children with disabilities, foreign nationals or LGBTI children. Lack of properly disaggregated data significantly impedes mitigating, identifying and counteracting discrimination.15 Analysis of the replies submitted to the Global Study questionnaire revealed that the most complete and detailed data are recorded for children in the administration of justice and children living in prison with their caregivers. At the other end of the spectrum, there 11 Cf. Chapter 12 on Children Deprived of Liberty in Institutions (1.2. Terminology and Concepts). 12 The impact of definitions and methodologies on the results obtained is best illustrated by the study conducted on the population of Syrian refugees in Lebanon. While only 1.4% of UNHCR-registered refugees were recorded as having a ‘disability’, the survey conducted by the CSOs revealed that 20% of refugees have an ‘impairment’. See: Help Age International/Handicap International, ‘Hidden victims of the Syrian crisis: disabled, injured and older refugees’, 2014, Available at https://reliefweb.int/sites/reliefweb.int/files/resources/Hidden%20 victims%20of%20the%20Syrian%20Crisis%20April%202014%20-%20Embargoed%2000.01%209April.pdf (accessed 15 September 2019). Similarly, in the State-party report submitted to the CRC-Committee in 2011, India indicated that the number of children with disabilities living in the country is between 6 and 30 million and disparities in the aggregate estimates are due to different definitions used by various actors collecting data. See: CRC-Committee, State-party’s report: India (2011), CRC/C/IND/3-4, Section 3B.3.1, p. 49. For the definition of ‘disability’ see: Chapter 7 on Children with Disabilities Deprived of Liberty. 13 CRC-Committee, General comment No. 9 (2006): The rights of children with disabilities, CRC/C/GC/9, 27 February 2007, para. 19. 14 Patrick Shannon & Maria Agorastou, ‘Identifying Children with Developmental Disabilities Receiving Child Protection Services: A National Survey of Child Welfare Administrators’, Families in society: the journal of contemporary human services, Vol. 87(3), 2006, pp. 351-357. 15 OHCHR, A Human Rights-Based Approach to Data: Leaving No One Behind in the 2030 Agenda for Sustainable Development, 2018, p. 7. 45