The unemployment rate is determined from information gained from surveys, not from hard data.
Only about half of those who claim to be unemployed qualify for employment insurance. Anyone on contract for instance does not qualify.
It is important to remember that the monthly rate merely shows changes from a baseline which may or may not portend a trend. The posted rate in itself can be misleading, especially in a low population area where a 10% unemployment rate may only be a few hundred people of whom only half qualify for EI, for instance.
Looking at the big picture it can help indicate the state of an economy. It's something like seniority in the workplace. It isn't always fair but what other way is there?