The national HBS is conducted on a monthly basis with different households surveyed during a specific month of the year for two consecutive years. For this survey, one subsample was surveyed in the same month of 2006 and 2007, a second subsample in 2005 and 2006. Data is collected through a monthly household diary and questionnaires. Since 2005 the households have been divided into five categories based on their socio-economic status. These categories are: employee households, farmer households, households of the self-employed, households of retirees and pensioners, and households living on unearned sources.