Introduction: The Sustainability of the World Population

Abstract

According to the UN projection 2017, the world’s population will increase by more than four billion in the next 85 years and will reach 11 billion by 2100. Quoting from Prof. Lam’s N-IUSSP essay, “The world’s next 4 billion” (Lam 2017), there is a debate on the future of humankind on the sustainability of ecological environments on the earth. However, if we take a closer look at this additional 4 billion people, most of the increase is expected in elderly (65+) and working-age adults (mostly older working ages); the increase in children and young adults is lower than ever. In the same UN projection, it indicates that Japan’s population will decrease from 0.13 billion in 2015 to 0.08 billion by 2100. Japan has entered a post-demographic transitional stage (Sato and Kaneko 2015), in which it will lead the world in population aging and decline. This chapter will analyze the world’s trends in Total Fertility Rate (TFR), Net Reproduction Rate (NRR), and Life Expectancy (LE) in comparison with Japan. The results show the world is entering the last phase of the demographic transition except in Sub-Saharan Africa and most of the world will be confronting a rapid aging and population decline. Furthermore, if the next 4 billion increase successfully by 2100, the demographic transition of Sub-Saharan Africa may also enter the final stage sooner or later. After then, the entire world’s population may be living in a “shrinking society” (Hara 2014).KeywordsThe sustainability of world populationUN projection 2017Population projection of JapanThe world’s next 4 billionTotal fertility rate (TFR)Net reproduction rate (NRR)Life expectancy (LE)Sub-Saharan AfricaPost-demographic transitionShrinking societyMalthus’ law