Final answer:
Societies in the last stage of demographic transition are characterized by an aging population, due to the decrease in birth rates and an increase in life expectancy as countries industrialize.
Step-by-step explanation:
The most characteristic feature of societies currently in the last stage of demographic transition is an aging population. The demographic transition model is a multistage model that describes the changes in population growth that typically occur as countries industrialize. Initially marked by high birth rates and death rates, societies in the transition eventually experience a significant drop in death rates followed by a decrease in birth rates, leading to an overall aging demographic as these rates converge at a low level.
In the last stage of demographic transition, common in high-income economies, the ratio of elderly individuals in the population increases due to low birth rates and longer life expectancies. This shift can impact economic structures, with a move towards fewer people working in agriculture and more in service and information sectors. Furthermore, it can lead to challenges such as the need for enhanced healthcare services for the elderly and potential labor shortages if there are not enough young people entering the workforce.