The problems have not retained their natural relative difficulty, which is why the introduction and falling costs of Air Conditioning have led to large migration to the Sunbelt.
That doesn’t follow. The sun belt became habitable because it got easier to fix, but that wasn’t asymmetric in difficulty, just asymmetric in relevance; the difference between ‘pretty easy’ and ‘very easy’ matters much less than the difference between ‘really hard’ and ‘a little bit hard’.
The problems have not retained their natural relative difficulty, which is why the introduction and falling costs of Air Conditioning have led to large migration to the Sunbelt.
That doesn’t follow. The sun belt became habitable because it got easier to fix, but that wasn’t asymmetric in difficulty, just asymmetric in relevance; the difference between ‘pretty easy’ and ‘very easy’ matters much less than the difference between ‘really hard’ and ‘a little bit hard’.