M2: slide 5: population

UN population projections: 3 most populous nations

- China, India, and US would be the 3 most populous nations in the future - increases in China's population (which is already well below TFR replacement levels) will be exclusively due to population momentum - for the US, immigration is expected to be the primary reason for increasing numbers - for India, both population momentum and fertility about the replacement levels will contribute to higher numbers

reasons for the projected increases in world population

- a desire for large families - a failure to achieve the desired number of children - population momentum

conclusion: UN population projections

- all 3 scenarios suggest that the world population is expected to grow over the next 50 years, but the size of the projected growth varies

UN: low population growth scenario

- assumes a future TFP well below the replacement level - the world population hits a maximum of 8.1 bn shortly before 2050 and declines to 6 bn by the end of the century

UN: high population growth scenario

- assumes that the world TFP does not reach replacement level - world population reaches 10.8 bn by 2050 - continues to expand over 15 bn by 2100

Industrial Revolution

- expanded the world's population carrying capacity - innovations in agriculture matched innovations in industry - this permitted labor to be transferred to industry while the productivity of the remaining agriculture laborers rose quickly to feed the growing urban population - better transportation by railroads and ocean shipping helped to transport food from surplus areas to deficit areas - modern medicine and sanitation also helped reduce the death rates/accelerate population growth rate

post WW2

- further improvements in food supply and disease control - modern techniques that were introduced in the developed countries were spread throughout the globe - both developed and developing worlds experienced a fall in death rates and a rise in life expectancy - most of the sharp rise in world population was contributed by developing nations

Malthus' Theory on Population

- people will generally not limit procreation below the biological maximum - if wages rise above the subsistence level, workers would marry younger and have more children, more of whom would survive - but this situation can only be temporary as a rise in wages would create an increase in labor supply which would create pressure on the fixed natural resources - eventually, due to diminishing returns, the food prices would rise and real wages would fall back to the subsistence level - if this process went too far, it would cause famine and death rates to rise - Malthus did not take into account that growth in food supply could stay ahead of population growth

observations of the history of world population

- population growth is only a recent event in human history - took more than 10,000 years for the world population to reach 1 billion in 1820 - the next 1 billion was added in about 110 years - for the last 40 years, 1 billion people have been added every 12 to 15 years

population momentum

- populations that grow rapidly have large number of people entering the fertile age brackets - even if these couples start having just enough children to replace themselves, the total population will continue to grow before leveling off (past fertility echo far into the future) - population momentum itself could add several billion people to the world's population in the 21st century

UN population projections

- projections consist of a variety of scenarios based on a similar set of assumptions about the decline of fertility but uses different assumptions about the amount and speed of the decline of fertility

what led to this unprecedented growth?

- the introduction of settled agriculture - during the years leading up the the Industrial Revolution, food supply grew and became more reliable - death rate fell/life expectancy increased - however, sometimes population growth was stalled due to famines, plagues, an wars

what determines population growth?

- the relationship bt annual births and deaths - the natural rise in population is given by the difference bt the crude birth and death rates - global scale: the natural increase in population = the population growth rate - national scale: population growth = difference bt rate of natural increase and net migration

UN: medium population growth scenario

- world reaches slightly less than the replacement levels by 2050 - world population rises to over 9 bn by 2050 - population growth then continues to slow leveling off at 10 bn by 2100

by 1800, the world's population had grown to almost 1 billion

implying an annual growth rate of 0.08% between 1 CE and 1800

by 1945, the population of the world was slightly less than 2.5 billion

so, the global population grew by 0.6% per year bt 1800 and 1945