My company uses the Bradford factor (BF) to assess your sickness absence patern. Basically the formula is
BF=hn²
Where h is the number of work hours missed (can also be days depending on the company) and n is the number of absence periods this rolling 12 month period.
My work has the first “trigger level” where they review your sickness absence at a BF of 1000.
What's the bit problem here you ask? Well if (like me) you have recurring problems that require sickness absence then the fact n is squared screws you very quickly. The other issue is people pushing themselves to get back to work quicker, then not quite being right suddenly again rack up their number of absences rather quickly.
I get that it's an attempt to put some objective measure into the process but it just doesn't work for a lot of people who find themselves hitting that trigger point rather quickly and having to justify their entire absence history rather than just the individual absences being assessed.