Warhammer 40,000: Zigzagged. - On the one hand, hive metropolitan areas quickly attain populations in the billions, but the motive they exist is that they are the only habitable (sorta) sites on the earth (generally a Death World, in desert, an ocean, or so polluted and/or radioactive even bionic units only last a few minutes variants), so a world of ten billion folks has them in three or 4 hives.