The size and composition of the world’s population matter in a number of important ways. The numbers affect food, water, poverty, environmental stress, children’s education, jobs, the needs of the elderly, and health services. Human population has grown very slowly for most of our history. Population studies show that earlier in our existence diseases were rampant, keeping life expectancy low and death rates high. It took until about the year 1800 for the human population to reach one billion. Then, in just 200 years or so, it has grown sevenfold to the current 7.6 billion.
For most of human history, the average human lifespan was considerably lower, with people not living past 50 years old. In the 17th century, England’s average human life expectancy was only about 35 years. Life expectancy began to rise in the 19th century with people living to about 50 years in the U.S .in 1900, and since then it has almost doubled. Throughout the early decades of the Industrial Revolution, life expectancy was low in Western Europe and the US. Many died from diseases such as typhoid and cholera, which spread rapidly in crowded and filthy conditions and from contaminated water.
From about the year 1850, a remarkable historic transformation took place that radically improved living conditions in industrial nations. Much of this progress was spearheaded by improved nutrition and most importantly by Public Health measures, e.g., improvements in sanitation, waste removal, the quality of the water supply, workplace safety laws, limits on child labor, and promoting nutrition through steps such as fortifying milk, breads and cereals. These measures strengthened people’s immune systems which in turn improved resistance to diseases. During this period there were advances in medicines such as vaccines for smallpox. The discovery of Tubercle Bacillus led to a vaccine for Tuberculosis. Another important discovery was that of antibiotics.
Decline in extreme poverty
In recent years, the United Nations, its agencies, and private humanitarian organizations have been pushing progress for eradication of those diseases in poorer countries with some success. For example, just since 1990, more than 100 million children’s lives have been saved through vaccinations, improved nutrition, and medical care. During this time there has also been a remarkable decline in extreme poverty (living on less than $2 dollars a day, adjusted for inflation). For most of history more than 90% of the world’s populations lived in extreme poverty. Now, fewer than 10% do. Still, much more needs to be done, too many children die from preventable causes, and still too many women die giving birth. Too many still have inadequate safe water and sanitation. The purification in water can lead to a remarkable decrease in disease.
The many brutal conflicts make ongoing humanitarian work much more difficult to deliver. It prevents the delivery of help and necessary supplies from reaching patients. In some cases nurses are prevented from entering places where they are needed, and those who are there have not been paid for 10 months. There are famine and outbreaks of cholera, which make humanitarian help extremely difficult.
The UN tracks population and revises its estimates every two years. The engine of demographic change is the “fertility rate,” i.e., the number of children that women have during their lifetime. In order for population to stabilize the fertility rate must fall below the “replacement rate” of 2, at which rate the population reproduces itself. Since the 1950s, fertility rates have dropped dramatically all over the world. The current rate is 2.5. In Europe the birth rate is well below the replacement rate and these countries are, in fact, losing population.
The 2017 UN population projection was based on the assumption that the fertility rate would continue to fall everywhere. In sub-Saharan Africa, however, the decline was slower than expected. The projections have been changed to reflect this.
10 billion people by mid-century
The current world projections are about 10 billion people in the year 2050, and 11 billion in the year 2100. This is an increase of over 3 billion people by the end of the century. Most of this growth will be in poorer, sub-Saharan Africa. The concentration of global population growth in the poorest countries is a formidable challenge.
Future population growth is highly dependent on the path that future fertility behavior will take. Small changes in fertility, when projected over decades, can generate large differences in total population. The key to stabilizing world population is the status of women. Presently, over 200 million women worldwide want and need contraception, but lack access to family-planning services. This can be alleviated tremendously when locally trained women are on hand to provide these services.
Dr. Sylvain Ehrenfeld, IHEU representative to the UN, and Dr. Reba Goodman, member of the Ethical Culture Society of Bergen County. Special thanks to Charlene Nicole Fulmore, assistant to Dr. Goodman.