The Earth’s population is predicted to rise form 7.2 billion in 2015 to 9.5 billion in 2060. This video from the Population Reference Bureau explains how technology, medicine, war, famine, and fertility rates impacts these numbers. The birth rate is decreasing but babies are still being born (of course), thus the population is expected to increase to 9.5B in 2060.
In the United States, according to the United Nations and The Economist, the population will look more column-like than bell curved in terms of population and age. The rate of birth is decreasing and the median age is increasing. From 1970 to 2015, the number of children born per woman was in a dramatic decline. Per John Parker, the Environmental Editor for The Economist, “For all of history, humans have lived in societies dominated (in numbers at least) by children. By 2060 children will be barely more numerous than any other age group up to 65. And looking after parents and grandparents will be as big a, or a bigger, social requirement as bringing up children and grandchildren. The year 2015 is, roughly, the halfway point in this astounding transformation.”
The populations in Japan and Nigeria can be visualized in this GIF. Japan has a similar trajectory as the United States except that the median age is higher. In contrast, he population growth of Nigeria is markedly different with an exponential expansion in birthrate creating a large young population.