Re: Wladimir Klitschko vs. Rocky Marciano
"Heavyweights are more widely recruited"
Here is a list from the 1952 Ring rankings of rated and Class A & B fighters--top 100--from outside the USA
Hein Ten Hoff--Germany
class A (top 50)
Johnny Arthur--South Africa
Class B (50-100)
Clearly it is a little more than the USA or UK (I will give you credit for meaning the British Empire thus including Canada and Australia)
Top heavyweights were coming from Western Europe and Latin America, and it is certainly possible that both areas were more active boxing centers then than they are now. Not only possible but likely.
One thing to consider is that the world population was much different then than now, with a far higher % of the population in Europe and North America than today.
The 1950's had champions from central Africa (Hogan Bassey) and Asia (Yoshio Sharai) but these areas did not impact heavyweight boxing back then.
**The Soviets and other eastern bloc countries did compete in the Olympics in the 1950's but did not do that well. There is no reason to suspect that there was some great fighter out there but unknown. This argument is the flip side of arguing that the Klitschkos would not be champions if the best American big men were not in the NFL or NBA.