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Eurostat uses the ultimate cluster approximation approach to estimate variance. The formulae apply for all sampling designs and they also apply for censuses. In case of a census, the weights whi are equal to 1 or slightly different from 1 (as consequence of non-response adjustment and calibration).
Eurostat considers the use of systematic sampling through the calculation of "computational strata" based on the values in the OSU_S1_* fields. * stands for CORE, LAFO, RDEV, AHMMetc. It does so in the SAS syntaxes, before applying the formula through the proc surveyfreq procedure. Actually, in order to reduce the computation time:
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