I didn't study the topic in depth, so take it with a grain of salt, but I recall reading something like this: * the % of people capable of highly intellectual

I didn't study the topic in depth, so take it with a grain of salt, but I recall reading something like this: * the % of people capable of highly intellectual work is quite low * as time goes on, more fields of activity require those people * you need a growing population to provide that supply They cited Russia as an example (population has been declining since the collapse of the USSR) - basically, to have e.g. a competitive aerospace industry in the 21st century, Russian population would have to increase by about 25%. This is just one example.