We can see from Figure 1.1 that the rapid increase in population in stages 2 and 3 of the DT begins to lessen as fertility rates decline. The birth rate levels off and can even decline as women, for a variety of reasons, have fewer children. But the legacy of the population spurt continues to flow through the population pyramid, first as a youth bulge, then as an increase in the middle aged, and finally into a top-heavy, aged and ageing population. In this chapter we examine these different bulges, including the youth bulge and the gender bulge and the possibility of a demographic dividend.

THE YOUTH BULGE

Population surges work their way through the demographic pyramid to create distinct bulges. The rapid increase in births because of a decline in infant mortality creates a larger than average cohort. At first, it is a large cohort of babies that then ages into a large youth cohort. Take the case of Jamaica. In 2001, the country's largest ten-year cohort was aged 0–10. This created a high youth dependency ratio with a consequent drag on economic performance as resources had to be devoted to a largely non-productive population. By 2011 birth rates had fallen and the largest cohort was now 10–20, and then 20–30 in 2021 as the baby boom turned into a youth bulge.

The youth bulge is generally considered a larger than average cohort aged between 15 and 29. This is an age when many people are either still at home or just starting their independent lives. There has been a lot of theorizing about this youth bulge. Revolutions and major social upheavals tend to tend occur more often with large proportions of young, frustrated men. Young people tend to have more energy than older people, and they often have less commitment to the existing order, being less bound by tradition and often critical of their elders. They are the basic raw material of social revolution and political violence. The German sociologist Gunnar Heinsohn (2021) was perhaps the first to promote the notion that an excess of young people, especially young males, leads to a greater tendency for social unrest, war and terrorism.