The estimation used information on the percentage of incorporated self-employed men and women with employees that was available for 1995,1997, 1999, 2001 and 2005 from the Contingent and Alternative Work Arrangements Surveys. For the missing years between 1996 and 2004, the percentage was derived through linear interpolation. For the years 2006 to 2011, the percentage for 2005 was used. The statistics have been developed by national statistical offices on the basis of EIP definitions, primarily by linking business registers to population registers or other administrative data.