Occasionally, such a scheme is complemented by another scheme, usually non-contributory, to cover unemployed persons who do not qualify for or are no longer entitled to unemployment benefits from the contributory scheme. Data from national household surveys (Labour Force Surveys in particular and Household Budget Surveys) can be used provided that employees contributing to an unemployment insurance scheme can be identified and that the number of persons concerned is sufficient to provide representative results (based on a sample survey). Establishment surveys can possibly be an alternative source, for example data from an employee benefits survey, ensuring an adequate coverage of employees in the survey. The source for the denominator will preferably be census data or Labour Force Survey data.