In predicting growth, demographers like to look at a country's "dependency ratio," a measure of how many old people there are, and how many young working people there are to support them. The particular ratio in the chart below measures how many old people there are in a certain country who are at least 65 years old per 100 people who aged between 15 and 64. If a country has a higher dependency ratio, then it means it has a more aging population relative to the young people.
In theory, the more young people there are, relative to old people, the better. From the chart, it is clear that emerging economies still have large room to grow.