Aging Europe
Although almost every country in the world is facing this critical problem, it is more severe to most European countries because their social welfare system is undermined. BBC has a report about German baby bust.
I believe many economists must have forseen such a issue long time ago. It seems it is difficult to find a balance between the welfare benefit and the government's fiscal policy. Many countries have been reforming their social security systems, but it doesn't save much. Will people become richer or poorer in the future? Let's hope we can find a solution before we know the answer.