NOTE: Since population data from the 2001 Census has been included in the results of the survey, the series of results returned as from the first quarter of 1998 were revised. Said revision did not apply to the third and fourth quarters of 1997. The microdata files for these two quarters, with populations referring to population projections based on the 1991 Census, can not be compared to the other data. Thus, quarterly files are only available as from the first quarter of 1998.