The only reason we have things like cell phones and super tankers that make it financially viable to have cheap gas is because the markets for the products are HUGE. If, for example, the population was suddenly, say two billion people instead of eight, a whole lot of things would either vanish or become staggeringly expensive. Instead of fifty products in each category, entire categories might vanish or just become very expensive. People who previously had lavish lifestyles would find them curtailed. It is only the huge markets that allow for nice, well optioned cars, for example. Entire countries like Germany, Japan and South Korea who rely on exports to survive would go broke. In addition, the depopulation might not hit the places the liberals want it to hit, like Africa, Asia and South America. (I know those are the targets because I used to be friends with a liberal who shared his hopes for humanity.) Oh, and forget about big budget movies. The audience will be dead.
Somehow, I get the feeling these elites haven't thought through this fully.