While looking at a group of international flags at the airport today it suddenly occured to me that all of the flags, no matter what country they were from, were the same shape. By that I mean they all had the same width to height ratio. Further, all of the flags I can remember seeing have also been in that same ratio.
Given that a flag is a unique representation of a country, why does no one have a flag that is a distinctly different shape? (Actually, I do seem to recall that someone has a square flag and maybe a triangular one but can’t connect them to a country right now; at any rate such variations seem uncommon.) Is there a “standard” width to height ratio for a flag? If so, when and why was that particular ratio selected and why is there so little variation from it?