I've posed this question several times in various threads where posters have stated that a lack of high-tier play is indicative of a poorly skilled player. I never get an answer.

Can anyone show me ANY statistical proof that there are more skilled players at the higher tiers than are found at lower tiers on the NA server?

Can anyone show me ANY statistical proof indicating increased difficulty levels at higher tiers?

The presumption here being that there are more better-skilled players to be found at the top tiers and so game play is therefore harder at these tiers than at the lower tiers.

Bonus Question: Can anyone define "difficulty level" in the context of WoT? Ie; what specific mechanics establish these "difficulty levels"