Why are there more zip codes than there are area codes?
The ZIP code is based on regional mail sorting centers. It does not depend on the population within a given area, but on the geographic area that the sorting center covers. An area code represents a collection of central offices arranged in a network. The middle three digits are exchanges (and you can have multiple exchanges on one CO switch). Theoretically, one area code can have 1000 (000-999) exchanges each capable of handling 10,000 (0000-9999) phones (or 10,000,000). Practically, not all exchanges and phone numbers can be used (e.g. 411, 911, 555-1212 etc.), many are reserved for technical reasons, and others are reserved for use as blocks of numbers for businesses. So area codes fill up as population and business activity expands, and new ones must be created. As a matter if fact, we kind of ran out of classical area codes some years ago — it used to be that an area codes could be easily as such because it had either a 0 or a 1 as a middle digit (201, 416). Those number ran out
