From a CBSA perspective, the shorter the period of time for the reporting, the less fidelity you'll have in the information. Having it on an annual basis, you'll have a much better picture of what's going on, because on a monthly basis.... It takes time to enter the removal numbers after the person's been removed. The people removed later in the month might not be captured in that information.
When the sample size is smaller, you'll run into privacy issues where we might have to exempt information. The smaller the numbers get, the more we run the risk of identifying the individual.