Eu-Silc is expected to become the EU reference source for comparative statistics on income distribution and social exclusion at European level, particularly in the context of the "Programme of Community action to encourage cooperation between Member States to combat social exclusion" and for producing structural indicators on social cohesion for the annual spring report to the European Council. The survey is carried out yearly, and provides both cross-sectional and longitudinal information. A rotational sample design is used. The use of 4 rotational groups allows to follow households up to four years. Household and individual characteristics are collected at the time of the interview, expenses refer to the last 12 months, while income reference period is usually the previous calendar year.