Just a note to make sure we are all comparing apples with apples, but US (and Australian) postcodes are much less specific than Canadian (and UK) postcodes.
AFAIK In Canada and the UK a postcode gives you an exact address, or pretty close to (around 10-20 properties to each postcode?). In the USA and Australia, a post code just gives you a 'suburb' (hundreds to thousands of properties to each postcode).
Some postal codes contain at least 5000 people, but at the same time my apartment building has one of its own.
I think it's largely based on how mail is distributed, as they are Canada Post identifiers. My 5000 person hometown has no delivery -- everyone goes to the one post office. But my apartment building has its own little postal box thing, which requires a key from the mailman, which is a special case compared to dropping in mailboxes on the rest of the street.
I don't suppose there's any postal workers on here to chime in?
Generally speaking, a postcode refers to a road, part of a road (if the road is very long), or a single organisation. Roughly, you will have 1-100 properties per postcode.
The first line of the address (often just the house number) and the postcode are sufficient to yield the entire address.
AFAIK In Canada and the UK a postcode gives you an exact address, or pretty close to (around 10-20 properties to each postcode?). In the USA and Australia, a post code just gives you a 'suburb' (hundreds to thousands of properties to each postcode).