Being an inevitable outcome of the demographic transition, population ageing will eventually knock at the door of each and every country worldwide. Despite the fact that population ageing is considered to be one of the greatest achievements of the humanity, it can bring along a number of threats apart from opportunities to the economical wellbeing of countries if preventive actions are not made in advance. A great deal of existing studies analyze population ageing while very few deal with its quantum and tempo. The findings of this research, based on the data for the period 1950-2100, answer the question of how sub-regions and selected countries in the world are differentiated in terms of quantum and tempo of population ageing: the lowest speed of population ageing is observed among European sub-regions whilst most of Africa is expected to age with a higher speed but not as high as Asia and part of America. High speed late ageing (with the speed between 0.18-0.30 percentage points where the proportion of older population aged 65 and older is to reach 14% of the total population only during the period 2050-2100) is the most common type inherent to all of Africa along with countries of Central and Southern Asia. None of the countries in the world would be ageing with a low speed at a later period of time. It refers to the fact that the processes of population ageing are accelerating further. The research findings also support the existence of close relation of the timing and extent of age structure changes in the context of population ageing. More recent demographic transition processes tend to result in the higher speed and shorter duration of population ageing.