Establishment surveys are not usually the best sources of data for disaggregations by demographic variables except in some cases by sex, thus often preventing the calculation of the pay gap for specific subpopulation groups. Within the European Statistical System, it has been agreed to use the Structure of Earnings Survey, a harmonised establishment survey on earnings, as the standard data source for computing the gender pay gap. Worker coverage of administrative records, such as social security records, often includes workers in paid employment who are covered by the administrative system.