I agree that systems don't have to be linear, but for it to be non-linear, it'd have to feed back somehow. Simply buying X times as many iPhones doesn't do it, unless e.g. those iPhones allow them to be Y times more productive, etc.
My point of view goes something like this: some parts of the world _are_ developed, and these already have the various additional productivity multipliers we theorised about above. These can be the baseline productivity level for our calculation. So if the rest of the world were to be brought to this level, the end result is indeed linear, and more or less depends on where we drew the line for "developed". However, it is not 1/1000th of the world population. We could be talking about a 10, or maybe 20x multiplier if we're very generous.
I also don't think historical precedent favours such optimistic numbers, though we could be living in interesting times. However OP's point was, again, a simple introduction / upliftment of more people, not technological multipliers.
My point of view goes something like this: some parts of the world _are_ developed, and these already have the various additional productivity multipliers we theorised about above. These can be the baseline productivity level for our calculation. So if the rest of the world were to be brought to this level, the end result is indeed linear, and more or less depends on where we drew the line for "developed". However, it is not 1/1000th of the world population. We could be talking about a 10, or maybe 20x multiplier if we're very generous.
I also don't think historical precedent favours such optimistic numbers, though we could be living in interesting times. However OP's point was, again, a simple introduction / upliftment of more people, not technological multipliers.