I agree except that what peaked in the period you refer to was INCOME mobility, and that, sadly, has got much worse since the 80s as all but a very tiny section of society have seen their wages stagnate. Ironically the old cultural 'tells' have become increasingly fuzzy in that period, though it can still be amusing to watched the impoverished middle classes attempting to maintain their wobbly barriers (eg latest fad for family holidays in beach huts!). We're all working class now.