Where I'm from, in Belgium, the standard condom size is 56mm. In the US, by contrast, the standard is 52mm; Magnum is 54mm and Magnum XL is 56mm. I haven't traveled much but this seems like the condom companies are motivated by sales so this is a good, maybe better, proxy for measuring a population's average penis size.

Please post:
-Country
-Most common available condom sizes
-Other comments

e.g.
Belgium
56mm
'Large size' here is only 57mm for some reason