IIRC these concepts are more relevant in a service-based economy.
In the Middle Ages, _land_ was the primary source of economic value. Fewer people means more land per person, therefore more wealth per person.
In the Middle Ages, _land_ was the primary source of economic value. Fewer people means more land per person, therefore more wealth per person.
Turn that now around, and kill a lot of people from the bottom 90% while letting the top 10% survive at higher rates. Suddenly, the world looks way more fair, even though the people at the bottom still have nothing.