If the "functioning countries" stay the same while the rest of the world catches up, the net result is -- drum roll, please -- growth! On a global scale! In fact, that would correspond to a global GDP growth of about 300%, or about 47 years at the current global GDP growth rate of 3%.

The more precisely you want to model the distribution, the more you can come up with all sorts of little technicalities. For example, if the rest of the world catches up to the developed countries without significant efficiency gains in many technologies, the environment is extremely screwed. We could go back and forth for days.

The question as posed was: does the world need to grow? The answer is a resounding yes.

You conflate them again! Do you even pay attention to he point I am making?

A developed economy should be stable, not collapse in on itself, if there is a period of no growth. It is disingenuous to try and prove your point by averaging out your income and economic issues with starving kids in Somalia!

Environment is already screwed. It's impossible to counterbalance consumption damage with increase in efficiency because you obviously can't have 300% efficiency.

Electric motor and generator are >90% efficient, most relevant technologies are ~50% and having diminishing returns.