Back after a long pause. Panel surveys traditionally interview respondents at regular intervals, for example monthly or yearly. This interval is mostly chosen for practical reasons: interviewing people more frequently would lead to a large respondent burden, and a burden on data processing and dissemination. For these practical reasons, panel surveys often space their interviews one year apart. Many of the changes (e.g. changes in household composition) we as researchers are interested in occur slowly, and annual interviews suffice to capture these changes.