Population dynamics: a century of growth, a future of decline Premium
Population dynamics: a century of growth, a future of decline Premium
Throughout the 3,00,000 years of human existence on earth, demographers estimate that approximately 108 billion people have lived so far. Remarkably, until 1804, the global population never exceeded 1 billion at any given time. However, this began to change with the advent of industrialisation and improved living conditions.
Today, at 8.2 billion (that’s 7% of the population that has ever lived on earth), the world’s population is at its highest point in history. Projections suggest that it will continue to rise, reaching a peak of around 10 billion by 2080. Yet, despite this upward trend, the emerging global concern is not overpopulation but rather the long-term implications of population decline.
For centuries, fears of overpopulation have shaped public policies. This narrative has shifted in recent years, with concerns about depopulation. As the world’s population is at its peak, this change in focus may appear paradoxical. This paradox underscores the need to reassess our understanding of demographic shifts and their consequences.
The debate over population growth began in the late 18th century when Thomas Malthus theorised that unchecked population growth would outpace food production, leading to famine and societal collapse. His predictions were echoed by scholars until the 20th century, including in Paul Ehrlich’s The Population Bomb, which warned of catastrophic consequences of overpopulation. Advances in public health, nutrition, sanitation, antibiotics, and the availability of birth control pills defied these doomsday predictions, fuelling population growth. Now, the conversation has shifted to the challenges posed by population decline for the first time in modern history.
Population depends on birth, death, fertility, and migration. Globally, net migration is zero unless we colonise Mars, leaving fertility and mortality as the main drivers. Total Fertility Rate (TFR) and Net Reproductive Rate (NRR) are key indicators that help predict future trends. TFR measures the number of children an average woman bears, and NRR measures the number of daughters an average woman bears in her lifetime.
A TFR of 2.1 is considered the replacement level, meaning each woman and a single living partner produce two children to replace themselves. The extra 0.1 accounts for infant mortality, stillbirths, neonatal deaths, and abortions. This TFR must align with an NRR of 1.0 for population stability, signifying each woman produces one daughter. A TFR of 2.1 and NRR of 1 ensure the population replaces itself across generations. The global TFR has dropped to 2.4 from 5 in the 1960s, signalling a potential long-term decline. However, regional variations complicate this picture. While South Korea reports a TFR of less than 1, and Uganda reports a TFR of more than 5, developed regions like Europe, East Asia, and parts of India have replacement levels with TFRs of 1.6-1.9.
A population age pyramid (see pic) is a visual and graphical representation of a population’s age and sex distribution. It provides insights into the demographic structure, indirectly reflecting birth and death rates. Its shape helps predict future trends, enabling policymakers to plan for resources like healthcare, education, and workforce development.
The demographic transition model explains population changes through five stages, each characterised by varying birth and death rates, which shape the population pyramid. In the high stationary stage, seen in countries like Nigeria, both birth and death rates are high, keeping the population stable despite high fertility rates. The population pyramid here is teardrop-shaped, with a broad base of young people and a sharp taper due to low life expectancy. In the early expanding stage, improvements in healthcare and sanitation lower death rates, but birth and fertility rates remain high, leading to an increase in population. Countries in this stage, such as parts of sub-Saharan Africa, show a pyramid with a gradually broadening middle.
The late expanding stage, seen in countries like India, features declining birth rates and very low death rates, with fertility rates nearing replacement levels. The pyramid begins to take on a rectangular shape with population growth. In the low stationary stage, as in the United States and Western Europe, low birth and death rates result in stable populations and fully rectangular pyramids. Finally, the shrinking stage is evident in Japan, where birth rates fall below death rates. If left unchecked, this will lead to an inverse teardrop pyramid from a rectangular pyramid with more elderly than young people and impending societal collapse.
The population pyramid takes a natural course from a teardrop shape to a rectangular shape and inverse teardrop shape in its natural cycle. The shift toward rectangular population pyramids reflects stability, economic growth, and improved public health, sanitation and nutrition. If unchecked, this trend will eventually turn into an inverse teardrop in the long run, with fewer working-age individuals, economic productivity declines, and dependency ratios increasing. Rising life expectancy without full health further complicates the issue. While people live longer, many spend these additional years in poor health, increasing healthcare costs and reducing quality of life.
India reflects global trends with significant regional disparities. Southern states report TFRs below replacement levels. In contrast, northern states including Bihar continue to grow. This diversity requires targeted policies. While some states need measures to stabilise growth, others must prepare for the challenges of ageing populations. India’s family planning programmes have succeeded in reducing fertility rates, but dismantling them is not a viable solution. Education, sanitation, and public health improvements have contributed to declining fertility, and reversing these trends in a developed society is unlikely to happen and will be harmful if it happens.
Given current projections, and barring catastrophic black swan events such as a pandemic or an asteroid impact, the global population will reach 10 billion by 2080. By then, most countries are expected to transition into stage four of demographic transition, characterised by low birth, death and fertility rates and a rectangular-shaped population pyramid. This demographic stability has been made possible by advances in antibiotics, birth control, sanitation, public health, nutrition, female education, and economic development. If any of these positive factors are disrupted, the economic prosperity achieved will not last.
But a greater risk lies in transitioning to stage five, where an inverse teardrop population pyramid—marked by a low birth rate and high death rate—could emerge, potentially leading to societal and economic collapse. To prevent this, governments should focus not on dismantling family planning programmes, but on enabling healthy life expectancies, where adults can live in good health with minimal morbidity and disability and remain productive for up to 75 years.
Investments in reskilling the geriatric population and research aimed at coupling longevity with productivity are essential. Global depopulation may not occur immediately, but localised challenges demand attention.
(Dr. C. Aravinda is an academic and public health physician. The views expressed are personal. aravindaaiimsjr10@hotmail.com)
