Calling in sick has always been a contentious issue, as we all know. I know it's beaten into NATS student ATCO at the college of knowledge that if you turn up to work you're admitting you are 100% fit and well. Should (heaven forbid) you be involved in an incident, it's not a defence or an excuse.
However, as has been mentioned, we all know of individuals that take things to the extreme. I'm sure that skews the stats a little.