You talk about the "relative privilege" of middle class people in developed countries as though the cause for their declining standard of living was other people having more, as if their "slice of pie" was being cut in pieces and given away. That's not how economic growth works. When China and India grow, the total productive power of the world economy grows. So now the world ought to be able to support "luxurious" standards of living for more people, but in fact we see fewer people enjoying such lives. So where's the output of all our work going, eh?
In China alone, hundreds of millions of people now have a middle class lifestyle that 50 years ago did not. I suspect that far outweighs the number of people in countries that were already developed 50 years ago who fell from a middle class lifestyle back to subsistence farming.
