That's just semantics. But by the same token, Something like 80% of Americans think of themselves as middle class. So it's not just the middle 20% or so.
What cannot happen is all of the world's population living as the American population lives right now. What can happen is for nearly all the world's population living in similar levels of comfort and material prosperity. What is needed is to reduce those aspects of the developed nation's lifestyles that are unsustainable, such as suburban sprawl and gas powered personal cars, and increase those things that are more sustainable, like livable, walkable cities with good public transit.
What cannot happen is all of the world's population living as the American population lives right now. What can happen is for nearly all the world's population living in similar levels of comfort and material prosperity. What is needed is to reduce those aspects of the developed nation's lifestyles that are unsustainable, such as suburban sprawl and gas powered personal cars, and increase those things that are more sustainable, like livable, walkable cities with good public transit.