while the implementation of 548 had the effect of allocating over 23 million numbers to a region of 2.6 million people, overlays have become the preferred method of relief in canada, as they are an easy workaround for canada's number allocation system. canada does not use number pooling as a relief measure. each clec is allocated blocks of 10,000 numbers (corresponding to a single three-digit prefix) for every rate centre where it offers service, even in the smallest hamlets. while most rate centres don't need nearly that many numbers, once a number is allocated to a carrier and rate centre, it can't be moved elsewhere, even to a larger rate centre.