In all three cases, it is apparently straightforward to characterise the ‘year’ over which receipt may occur. This is largely because of the nature of the data sources: the Dutch and the two Swedish studies are based on administrative record data from income tax sources and the SLID, used by Hansen and Lofstrom (2011), also utilizes administrative record linkage as the source for income for many respondents. ( Income and taxes are assessed over a one-year reference period.)