Of the world's population under 15 years, the majority lives in __________.

The majority of the world’s population under 15 years lives in Africa due to several demographic factors. Africa has a high birth rate, leading to a larger proportion of its population being young. This trend is reflective of the continent's overall population growth, where many countries experience significant youth bulges as a result of lower mortality rates and higher fertility rates.

In contrast, regions like Japan and England have aging populations with declining birth rates, resulting in a smaller proportion of younger individuals. Haiti, while it does have a younger population compared to some developed countries, does not have the same scale as Africa. Thus, the correct answer highlights the significant youth demographic concentrated in Africa, showcasing its role in global population trends.