When I asked the original question, it was because I have been buying bats for 25 years and while the shapes have changed, the volume of wood on a 2-10 bat is basically the same.
Bats now have bigger edges, but are concaved rather than convex.
The likes of Barry Richards used a 2-3 or 2-4 bat. Of course they are going to be thinner.
But I don't believe the heavy bats Goochie and Botham used were, in terms of volume, any different to the bats today.
The point really is that bats are pressed better now.
Having said that, I don't believe there is any difference in performance from my first county bat to any bat I can get now.
I believe that the balls get hit further etc mainly because batsmen are much fitter and stronger, plus players practice better now and the boundaries are much smaller.
Moaning about bats is a red herring.