People on permanent contracts take twice as many sick days as people on temporary contracts, Trouw reported on Friday.

According to a report by research institute TNO, absenteeism through illness among people on temporary contracts is 2% compared to 4% for people with permanent jobs. This means people on permanent contracts are absent through illness an average four days of every hundred working days.

People on zero-hour contracts, temporary agency workers, the self-employed and free lancers also take fewer sick days.

Selection

TNO says one reason for the discrepancy is that employers select workers based on the state of their health. Temporary workers who have frequently called in sick are not as likely to be offered another temporary contract. Age is another factor: people on temporary contracts tend to be young and therefore generally healthier.

The self-employed and freelance workers who take sick days feel the consequences in their own pocket and therefore have a strong incentive to keep working, the report says. They are also under less pressure because they have more freedom to schedule their work.

Exceptions to the rule are the self-employed who work in trade, business services and transport who take even more sick days then their permanently employed colleagues. TNO says this may be because they are not as independent as their status might suggest and that they are doing the same jobs in the same circumstances as their colleagues.