I find it hilarious that Australia has just 4 digits in its post code. The US has 5 digits with 4 optional digits. Taiwan (a much smaller place) has 3 digits with 2 optional specifiers.
Singapore has 6.
Singapore has 6.
Australia's post codes, on the other hand, are really wide. The entirety of central Sydney is all "2000" and mine covers around 6 city suburbs.