What is the minimum earth population required to keep up the current technologic state of the art long term?

Question

I'm wondering what would be the minimum number of people living on earth required to keep our current level of technology, e.g., in each field the state-of-the-art. Many technologies have long dependency chains, e.g., to run a nuclear power plant, besides the people running and maintaining it, it needs to be built at first. In order to build the power plant, we need to be able to produce steel etc. In order to produce steel, we need machines that can extract raw resources (e.g., ores) from the planet and also we need power in the first place to melt the ores, etc.

Besides these technically required resources, there are also other things required in order to maintain our technology level, e.g., we need people who can control the machines short-term, but also long-term people that are able to teach the required knowledge to other people, which in turn are able to build or run these things.

So, given all these partially multi-directional dependencies, what would be an estimate of how many people do we need to keep our standards?

Answer 1

This depends very much on which people are included in that "minimum population" and how closely they're concentrated. A quarter billion could probably do it in a space like the continental United States -- that's about what our population was twenty years ago (Alaska and Hawaii don't count for population on this scale; the two combined equal one large city metro area). This would still assume spread out some

On the other hand, if they're spread over the entire Earth, I expect it would require a minimum of about two billion, possibly twice that, to keep what we (as a world) already have. This is both from the standpoint of production (takes so many people just to feed the ones who produce technology, for instance) and that of demand (you can't maintain, say, a thriving market in smart phones if there aren't enough people needing smart phones to keep the network up).

Guesswork, of course; I'm neither a working technologist nor an economist (and economists are famous for never arriving at the same answer from the same data).

Answer 2

Not all countries and companies have the same technology so I think you have to pick what technologies you want to keep, take the population of a country which has the closest set but smallest population and then add the employees of the companies that posses the remaining technologies you want to keep. Keep in mind though that some technologies will become unneeded without appropriate demand. Also I strongly suggest keep Europeans or north Americans to maintain the level of science.