Sickness absence is calculated as the amount of absence days divided by the amount of annual working days. The number of working days in leap year 2008 was 215 for full-timers and 43 for people who work one day a week. Sickness absence figures are based on the National Survey Working Conditions (NEA). The sickness absence rate according to NEA varies only marginally from the quarterly survey on sickness absence conducted by Statistics Netherlands.
The NEA is a large-scale survey conducted among employees in the Netherlands. The NEA surveys working conditions, nature of the job, labour relations and terms of employment. The NEA is conducted by the Netherlands Organisation for Applied Scientific Research (TNO) and Statistics Netherlands. More information on the NEA is accessible on the website of TNO.