It is interesting that world wide 80% of gold comes from open pit while in Canada it is mainly deep underground mining; the question is why?

1) I know that for copper and nickel there are more oxidic ores in hot and humid climates while sulfide ores are common in Canada, Russia

2) could it have to do with vegitation, in a heavily vegitated(trees, bush) area it is harder to see out crops

3) in more populated and poor areas, people live more off the ground, maybe they also find ores more easily

4) maybe in Canada we are mainly focusing on equipement and highly trained geologists looking for veins, etc

any other thoughts why there is such a difference