In addition, when entire households emigrate outside the country, they fall out of the sampling frame making it impossible to capture them through household surveys conducted in the origin country. All operational criteria of forced labour have to be customised according to the national context in order to be relevant to the situations of forced labour existing in the country and they also have to be consistent with the national legislation on forced labour. The framework for the identification of forced labour and its elements on the basis of the operational criteria is part of the methodology proposed by the ILO.