Ranking high # series by degree of difficulty (and why?)

[kailes2872]

Now that I am close on my post war set run, I was wondering if anyone had an opinion on the high numbers. Difficult is a relative term because they all seem readily available- it is just that some cost more than others. What I am wondering is why? We obviously know the ‘52 high story - but what happened in ‘66 and ‘67 that didn’t happen in ‘65 and ‘68? Why is ‘69 easier than ‘70?

I would rank them -
Tough (much more expensive than low # commons)
‘52
‘53
‘67
‘66
‘62
‘61
‘55
‘72
‘70

Tougher than normal but not as out of control as the first group
‘59
‘57 (mid)
‘71
‘63

Not much of a noticeable difference
‘54
‘56
‘58
‘64
‘65
‘68
‘69

It has been a while since I built some of the sets so my memory fails me a bit on ‘64 and ‘63

For those who collected these out of the packs, did something different happen in the tough years? Late issue? Better than average football set that diverted attention? I understand the concept of the high series and why collectors might have lost steam, I just don’t understand what makes one year more expensive than another. With the exception of dumping them in the ocean I would expect similar relative scarcity.

Thoughts? Your ranking of toughness?