This Great Graphic comes from the World Bank. While we are all familiar with the demographic shock in the high income countries. For a few years already, Japan is experiencing a shrinking work force and a shrinking population. Part of Europe, such as Italy, does not seem far behind. The retiring of the baby boom generation and the declining reproduction rates are generally well known.
What is new about this graph is that it shows that the developing, especially Asia and Latin America, are approaching their own demographic challenge in the form of aging populations. In China's case, as a consequence of the one child policy, the question has already been asked whether China will get old before it gets rich.
Note too that, as a species we are living longer. There the gap in longevity between what the World Bank calls the developing and developed regions has narrowed at higher levels and this is project to continue, albeit slowly, over the next few decades.
The claim that in 2050 80% of the world's older people (60 years and over) will be in the emerging and developing economies is striking, but perhaps a bit misleading given that the vast majority of people live there. Moreover, the gap between the size of the population in the high income (developed) countries and lower income countries (developing and emerging) countries is project to also widen.