Over the last century we see many people (across the globe) taking advantage of readily available paper credit and subsequently used it to 'invest'(speculate) into stock markets, tech markets, housing markets, bond markets, oil markets, ...etc. and the graph for these markets would rise dramatically eventually to a point were everyone starts to realize that it's a bubble.
Now do you think the same thing is also occuring with the human population?
Do you think there is a bubble in this 'market' because of too much "levaraged investing"?
People in the past taking on paper credit and borrowing their way to start family and having children?
Their "investment"(speculation) was in children instead of stocks.
Children were conceived and were raised thanks to the IOUs borrowed on behalf of their own future income.
So today when we have all the young adults complaining about how there are not many jobs, and the ones that are available are not a high paying one, technically wasn't this expected?
Money was borrowed from their future income in order to concieve them and raise them.
Now the birthrate of many nations is slowing down.
Is this a classic sign of a bubble 'market'?
http://www.ipsnews.net/2015/02/analysis-mega-cities-mortality-and-migration-a-snapshot-of-post-u-n-world-population/
http://www.bbc.com/news/magazine-16472310