Many around the globe are starting to wake up to the fact that this century humanity will face an unprecedented transformation: the global population will stop growing and will start to enter a period of sustained and longterm decline. As the Atlantic reports, it is true that there have been demographic blips before, when the global population has dropped. For example, the Black Death in the 14th Century is thought to have killed about 200 million people, a significant proportion of the population at the time. However, the upcoming demographic decline will be different. This time, instead of massive numbers of people dying in a short space of time (Black Death, Mongol invasions, World Wars), the population will decline because birth rates have slipped below replacement rates.

The reasons behind this transition to a low fertility world are beneficial: rising incomes, rising levels of education for women, and urbanisation. However, the outcome of a demographically declining world is something that we have no experience of. For most of human history and pre-history our numbers have been growing: very slowly at first and then much more quickly in the last 100 years or so. Thus, 12,000 years ago there were perhaps 4 million humans on Earth. 2,000 years ago there might have been 190 million people. As little as 200 years ago, there were still fewer than one billion people worldwide. There were 1.65 billion people in 1900 and then an explosion: 6 billion in 2000 and 7.7 billion today. Thus, we know about global population growth, we just don’t know what global population decline will mean.

The UN estimates that we will start declining by the end of this century, although others estimate that it will happen much sooner than that. We’ve reported other demographers who estimate that the switch will occur around the middle of this century (in our lifetimes perhaps!) There is always the chance that the projected decline will not occur due to a surge in fertility rates, but this seems unlikely. In the last 50 years the global fertility rate has halved and the trend is still downwards. Furthermore, once you have a society in which small families are the norm then there are many barriers to suddenly having more children: everyone’s experience is of small families; while society, the economy and even cities are designed for one or two-child families. Perhaps there will be some political calamity that will see whole societies shift to having more children, but I can’t see it happening anywhere in the West at least in the foreseeable future.

But what we can predict with some certainty is that, by the time the global population stabilises and then starts declining the most numerous world region will be Africa and the largest religion will be Islam. And we will be much older. There will be six times as many people aged 80 or older and the world’s median age will have jumped from 31 to 42 years old.

Many more countries will face the same problems of Japan: a greying, declining workforce and hard-to-service national retirement and health programs. The answer might be large-scale migration (which brings its own problems), or encouraging more women to enter the workforce (which adds another barrier for increasing a nation’s fertility rate in the future). At a more micro level, children will generally have fewer siblings and will receive a greater share of their parents’ time, energy, stress, expectations and resources. Not only will there be fewer familial relationships, but the financial support and diffusion of financial risk that a larger family network give will also decrease.

Although these trends are discernible across the world, it is important to remember that each nation will face these issues at different times. (That is why Japan’s experience should be so keenly watched elsewhere.) Fertility rates differ between countries and each nation’s experience of population stabilisation and decline will come at a different time. (Some countries will probably still be growing into the 22nd century). Some will weather the social and economic effects better than others. Some nations may not weather them at all.

Marcus Roberts is co-editor of Demography is Destiny, MercatorNet's blog on population issues.

Marcus Roberts was two years out of law school when he decided that practising law was no longer for him. He therefore went back to university and did his LLM while tutoring. He now teaches contract and...