What would be the best way to determine if a particular keyboard character is available/convenient (enough) for most/all end users to type, regardless of keyboard layout?

For instance, if I want to determine if the character `~` will be hard/impossible for a set of users to type somewhere in the world (given its placement on the keyboard), how would I best determine this?

Is this something that can be accurately determined; and further, is this something I should be worried about?