Population studies examines human and non-human populations and how they change over time. Key aspects of population studies include migration trends, urbanization, age demographics like aging populations and birth rates, and their environmental and economic impacts. The global population has grown exponentially from around 7 million 12,000 years ago to nearly 9 billion today. Most of this growth occurred in the last 200 years as birth rates declined. Currently, over half the world's population lives in countries at or below replacement fertility rates. By 2050, the world's population will continue growing but more slowly, with more elderly people and increasing urbanization especially in developing countries.

1. POPULATION STUDIES

2. Why Population studies
• Migration
• Rural Urban
• Urban Rural
• International
• Baby boomers (reproduction)
• Ageing
• Ecology

3. PROBLEMS IN POPULATION
• Billion people are chronically hungry.
• A billion people are living in slums.
• Billion pple need Education 2/3 (women)
• 215 women (problem with contraceptive)
• Past, present and future of the human
population.

4. POPULATION
Therefore Population studies is the
phenomenon associated with the learning of
humans and non-human species that
includes viruses like influenza, the bacteria in
your gut, plants that you eat, and all
domestic animals

5.  And it includes non-living objects like
light, trains, and taxi cabs and buildings
 And it includes the study of these
populations .

6. Population studies is the central subject
related to economics, to human wellbeing as
in material terms; related to the environment,
to the wellbeing of the other species with
which we share the planet; and the wellbeing
and culture which affects our values and how
we interact with one another.

7. World Population: The Past
 Agriculture between 6,000 and 14,000 years
ago, the human population, has grown 1,000
fold from approximately seven million to
nearly nine billion this year.

9. Number of people in the world –
Nearly nine billion

10. Over the same interval, the earth is the same
 The continents haven’t expanded 1,000 fold or at
all.
 The oceans are the same size as they were
before.
 The atmosphere is the same size as it was before.
So the question that concerns a lot of people and
me is whether the impacts that seven billion
people or more in the future will have on the
earth will endanger, will threaten our own
wellbeing and the wellbeing of other species on
the earth.

11. We know that humans have already caused
the extinction of many species.
The question is, is that going to come back
and bite us, and if so, in what ways?
Population studies provides us with a reliable
way to imagine and to reimagine the future.
S About 2,000 years ago, there were roughly a
quarter of a billion people on the planet.
Today, there are almost nine billion.

14. More than six-seventh of the growth since the
beginning of humans 50,000 years ago has
occurred in the last 200 years.
Quarter of a billion to half a billion took 16
centuries.
So we reached about half a billion humans about
1600, more or less.
 The population of the earth, the human
population, if it were growing exponentially would
go from a quarter billion to half in 16 centuries
and from half to one in another 16 centuries.

15.  Human population of the earth reached a
billion around 1800.
 Because of food stuffs that came from the
New World to the old; notably potato and
corn or maize.
 And because many of the people who were
overcrowded in Europe went to America
where there were fertile and unoccupied
lands to use.

16.  The Columbian exchange across the Atlantic
liberated population growth in the European
sector, there was a similar development in
Japan, an acceleration of population growth
around the same time.

17. In 1800, the Industrial Revolution began and
the population doubled from one billion to two
billion by 1930.

18.  Next doubling from two billion to four billion
took only 44 years, 1974.
 But for the Black Death in the 14th century,
in the last 2000 years saw upsurge of
population growth
So in absolute terms and in percentage terms,
the number of people we are adding to the
planet has begun to slow in recent times.

19. Fertility is the Key to Understanding
Human Population?
Since 1950, humans have made the swiftest,
voluntary change in reproduction in human
history.
 Around 1950 the average number of children per
woman, per lifetime was very close to five.
Today, the average number of children per
woman is about 2.5 or 2.6.
In other words, billions of people have changed
their reproductive behaviour to lower the
number of children born in a lifetime from five to
two-and-a-half, but not everywhere.

20. World Annual Growth Rate in %

21. In Sub-Saharan Africa, the decline has been much
less. From perhaps 6.6 children to 5.1 over the
half… the second half of the 21st century.
To understand the consequences of this fall to
two-and-a-half children per woman, you need to
know what is meant by replacement level fertility.
 So I am going to introduce that by telling you
about the theory of bathtubs.
 A regular bathtub with no stopper.

22. theory of bathtubs.

23. The bathtub approach

24. So two things happen with a bathtub with no stopper.
 Water comes in and water goes out.
 And you can see intuitively that if the amount of water
coming in per minute exceeds the amount of water
going out per minute, the level of water in the bathtub
is going to go up, and if the amount of water comes in
per minute is less than the amount being drained out,
the level in the bathtub is going to go down.
So the amount of water coming in that just matches
the amount going out keeps the level of the bathtub
steady.
Okay? That’s replacement level bathtub water.

25. Now, water coming in corresponds to births to
the earth.
 And water going out corresponds to death.
 And the level of the bathtub corresponds to
the total population size.
 So, if the number of births just matches the
number of deaths, the population stays steady
and that’s the replacement level of fertility.

26. Now, you’re asking yourself, what is the replacement
level of fertility? The answer is, it’s about 2.1 children
per woman.
There has been an amazing transformation in the
distribution of fertility across the world.
In 2003, this was not in any newspaper anywhere, but
it was a very important event.
 In 2003, half of all the women in the world were
having replacement level or less.
And now more than half of humanity lives in a country
at or below replacement level fertility. It’s the first time
in human history that this has happened.
 And it’s important.

27. But you remember that the total fertility rate,
the average number of children per woman is
at 2.5, not 2.1.
 And that’s because on this curve, the green
curve, the folks with high fertility are further
to the right of the red line than most of the
folks with low fertility are to the left.
So the average is skewed to the right.
 So we still have a growing population.

28. But this change is continuing and how fast it
continues is something that as potential
scientists, as citizens will influence by what
you choose to do about the 215 million
women who have an unmet need for
contraception.

29. World Population: The Present
 The present.
This is a population pyramid.
 It is one of the basic descriptive tools of
POPULATION STUDIES and you should
understand what it is.
Let’s start with the left side of the picture.
The horizontal axis, the width of the bar tells
you how many people there are and the
vertical axis correspondence to age group.

31. Comparing Rich and Poor countries

33. So the lowest bar is for people aged zero to
four with males on the left and females on the
right.
 The next bar is people age five to nine.
The top bar is 95 to 100.
 And what you see is that in the rich countries,
there are about as many people aged, let’s say
zero to four as there are aged 85 or 90, but it’s
basically a slender column.

34. Now compare it with the age pyramid for the
poor countries.
 The base of the pyramid is enormous
compared to the number of elderly.
So there are many more workers to support
the elderly, per elderly person.
The width of the bar, again is the number of
people, so in the ranges from five to 14 of five
to 19, that’s the school age population.

35. It means that the challenge of educating those
children is much greater in the developing
countries than it is in the rich countries because
those bars keep getting wider as the developing
countries pump in more children at the bottom of
the pyramid and the age groups move up with
time as they get older.
And so the larger school age population is
followed 10 years later by a much larger military
age population.

36. • So if you look at the age groups 19 to 30 or 15
to 30, whatever the legal ages or illegal ages
are for fighting, you can see that the potential
military force in the developing countries
vastly exceeds that in the rich countries.
• It doesn’t mean it’s military power for them,
it means they can afford a military
engagement in a way that the human
resources of the rich countries make very
difficult, increasingly difficult.

37. • So where is the growth going? The demographic
growth is happening in the countries that can
least afford to deal with the additional
population.
• What’s the average income?
• The reason we call a rich country as rich is that
their average income is about $32,000 a year per
person and in the poor countries it is about
$5,000 a year.
• What fraction of people are living on less than
$2.00 a day? Nobody lives on less than $2.00 a
day in the rich countries and 51 percent, just
about half in the poor countries.

38. • In other words, about 3.5 billion people on
our planet are living on $2.00 a day or less.
• So you might ask yourself, if things are so bad
there how is it that their population is growing
so rapidly?
• And the fact is that the difference in death
rates is much smaller than the difference in
fertility rates.

40. • So even though a higher fraction of children
die before they reproduce, the average
number of children that people have when
they do reproduce in the poor countries more
than compensates for the increase in the
death rate.
• So that’s why we have rapid population
growth at the same time that we have high
fertility, high mortality because we had even
higher fertility.

41. Fertility rate of developed and
developing countries

42. • The global economic inequality means that
the most rapid demographic growth is
associated with the people who have the least
means to take care of the children that are
born and the people with the greatest need
for reproductive healthcare and services have
the least means to afford it.

43. • It’s an important general question, how does the
rich world benefit from the prosperity and
development of the poor world?
• There are lots of different answers you can give.
• One is, purely economic.
• Richer people in China and Africa will buy more
American music CDs and more movies and more
software and more high tech engines from
General Electric and more products because they
have more means to buy.
• So that’s one kind of an answer.

44. • A second is public health.
• There are millions of flights in both directions from the
poor countries to the rich countries every year.
• And the microbes don’t know about passports.
• And they cross from Bombay or Mumbai to New York
just a fast as they go from New York to Mumbai.
• And when there are outbreaks of drug resistant
tuberculosis, those can travel around the world and
they pose a danger to me and to you guys.
• So we have an interest in the health and wellbeing.
• A direct, personal interest in the health and well-being
of people in poor countries.

45. World Population: The Future
• So now we’ve talked about the demographic
past, and the demographic present.
• And next we’re going to talk about the
demographic future.

46. • Woody Allen said, “Eternity is very long,
especially near the end.” So, we’re not going to
talk about eternity.
• How much of the future is relevant to you? Well,
according to the United States Life Tables,
published by the National Center for Health
Statistic, an 18-year-old in the United States in
has a 91 precents chance of surviving to 2050, 91
percent, based on survival rates in 2006.

47. • If you behave wisely and if economic and
medial progress continues, you have at least
that good a chance of making it to 2050.
• So we’re going to talk about the world from
now to 2050.

48. • World’s population will get bigger.
• It will grow more slowly.
• It will be older in the sense that the fraction
of older people will increase dramatically
• It will be more urban.

49. The Future of The World’s
Population: Bigger
•
Fertility Assumption.
• And it shows that the world would go to
about 11 billion people by 2050.
• However, if fertility drops as it has dropped in
the past, the medium projection of the U.N. is
9.1 by 2050

52. • We can put in place fertility control mechanism to
achieve about 2 billion decline, (UN,2019)
• What we do between now and 2050 will have a
huge impact on how difficult it is to feed, house,
shelter, educate, and provide health for the
billions of people on the planet in 2050.
• It will affect an enormous range of human
problems.
• It’s possible that population growth would end
before 2100 depending on the choices we make
now.

53. • What choices am I talking about? Choices like,
educating women, providing credit to women in
countries where women are not now allowed to have
credit.
• Providing reproductive healthcare so that women are
not forced as they are in some countries to have
children when they don’t want to.
• Raising the age of marriage so that 12-year-olds, 13-
year-olds and 14-year-olds aren’t put into marriage.
• There’s a lot of things we can do to raise people,
including even women, raise people’s control over their
own lives

54. • your mandate is to focus on quality of
children rather than numbers.

55. The Future of The World’s Population
: Slower Growth
• So the first fact about the future is that the population
is going to get bigger and the second fact is that the
population is going to grow more slowly depending.
• By 2050 in the medium projection from the United
Nations Population Division, the world will be growing
by 31 million people a year.
• What’s it doing now? It’s growing by 76 million people
a year.
• In the poor countries, the population will be growing
by 32 million a year while in the rich countries the
population will actually be declining by a million
people a year.

56. • Already today , population is declining in more
than 50 countries.
• What’s happening here is a shift in
childbearing desires and action from quantity
to quality
• as people urbanize, as people get educated, as
wealth improves, people are making greater
investments in a smaller number of children.

57. The Future of The World’s Population
: Older
• The next is aging. So by 2050, there will be
about three times as many elderly as
children.
• This is the first time in human history that the
elder population has outnumbered the young
population.
• So what? Well, aging affects energy demand.

58. aging

59. • So even if you are interested in the environment,
you need to know about the age structure of
populations.
• Older householders spend, at least in the United
States, India and China, the three countries
where it’s been studied in detail, spend more
than younger households measured by the age of
the head on utilities services and healthcare.
• Utilities are the most energy intensive part of the
household budget.
• That’s not the only reason to care.

60. • The rise in the fraction of elderly poses an
increasing challenge to a relatively reduced
number of workers.
• And it’s possible that the well-being of elderly
people could improve, if they’re educated or
could get worse if they are warehoused in old
people’s homes.
• We know for example, that people who are
educated in their youth have much lower
disability when they get older.

61. • And in fact, disability rates at any given age in
the United States have been dropping by
about one-and-a-half percent per year for the
last 25 years.
• So there are far fewer disabled elderly now
than there used to be.
• People are healthier at older ages.
• That’s the result of investment in education in
youth.

62. • So, there are policy implications for a rising
aged population, we better invest in educating
people when young.

63. The Future of The World’s Population
: Urban
• And the last of the four topics is cities.
• In 2000, you could divide the world into two
equal parts; half rural and half urban, about
three billion rural and three billion urban.
• In 2050 the rural population will still be at
three billion and the urban population will
have doubled from three billion to six billion.
• All of those additional three billion urban
people will be in poor countries.

64. • Poor countries need to accelerate quality of
urbanization
• So what’s the consequence? What does this
massive shift towards urbanization mean?
• If we under invest in cities, we can go from a
billion people living in slums today to four billion
people living in slums.
• And if we invest in the cities, if the real estate
companies realize the opportunities, the
incredible demand that people have to live in
decent housing, we could reduce the size of the
slums.

65. • urban policy and decisions will lead to:
• Infectious diseases spread
• Warfare in the cities.
• Disorder,
• Clean water supplies;
• Security for people in their houses.

66. • Urban areas have lower fertility rates.
• improved education
• Higher use of Morden contraception
• Lower umet needs of contraception
• Concentrated economic productivity

68. • Now, a six meter rise would happen if the
Greenland and Antarctic ice masses melted.
• Six meters is about 20 feet.
• And it would be completely underwater.
• So that would be a terrible thing to happen.
• Urban growth could affect the food supply.
• Right now, cities occupy three percent of the
land surface of the earth.

69. • The land, the arable land, the land where we
can grow food well is about 10 or 11 percent
of the land surface of the earth.
• It’s not surprising that many cities are smack
in the middle of the best arable land because
that was where a food surplus could be easily
produced without having to ship the food.
• Now, if cities are going to double, we have
another choice.

70. • Do we double the area from three percent to
six percent and eat up our arable land, literally
or do we double the density and keep the
areas of the cities constant at three percent?
• This is a choice for the future and it depends
on zoning and culture and real estate
developers and economics and choices that
we make as citizens.

71. Conclusion – Food: The World Is
Running Out Of Resources To Support
Its Growing Population
• How do we address the problems that we have?
• There are three kinds of solutions that people
have put forward; bigger pie, fewer forks, better
manners.
• The bigger pie people say we should use
technology to increase production.
• The fewer forks people say, we should use
contraception to reduce population growth and
we should consume less material products.

72. • And the better manners people say, we should
eliminate violence, inequities between men
and women, inequities between rich and poor,
inequities between young and old.
• We should eliminate rational subsidies and
just make things work more efficiently.
• Get rid of corruption.

73. Educate all children, boys and girls, well for 10
to 12 years, high quality, primary and secondary
education.
Improve ecological sustenance

74. • So the question I want to address now is can we grow
enough food to bring us to 2050 without catastrophe?
• These are data from the Food and Agricultural
Organization in Rome.
• They are estimates of the number of people in the
world who are chronically under nourished day after
day.
• The current estimate is about 925 million
people. That’s nearly a billion and it is higher than the
number has been in the last 40 years.
• Ninety-eight percent of these people live in poor
countries. Not only poor countries.

76. • So the question you should be asking yourself
is, well aren’t we growing enough
food? What’s the problem?
• We’ve got nine billion people and there are a
billion of them hungry.
• The answer is, less than half of the grain that
we grow goes into people’s mouths.
• Divide the world’s grain into six equal pieces.
• One piece we use to make biofuels, starches,
for seed and other industrial uses; plastics.

77. • Two-sixths, we feed to our domestic animals of the rich
people, those who have the means to afford those
animals and meat products.
• Less than half, the other three-sixths goes directly into
human mouths.
• We could be feeding 11 billion, but we only feed half of
that amount, 5.5 billion into human mouths.
• We put machines and animals in line before people
who don’t have money to express demand in markets.
• Hunger does not fit into our economic theories.

79. Conclusion – What’s The Solution?
• So, here are sugestions on how to solve the world’s
problems.
• Eliminate all unintended pregnancies and plan for lives
• Economics, open credits and markets to small
farmers. A majority of the world’s farmers are women.
• They are the ones out in the field actually doing the
work.
• Eliminate perverse subsidies in rich countries make it
very difficult for poor farmers to enter markets
because they lower the price in artificial ways.
• And let’s raise the incomes of the poor.

80. Environment.
• Use the best farm lands for farms and
internalize the external costs of agriculture.
• Get rid of the pollution and use chemicals in a
way that doesn’t damage the environment.
• And fourth, promote healthy diets and value
adequate nutrition for every person.
• Not only for the industrial crops that fund our
biofuel habit, but for the crops that provide
food to the poor.

81. Conclusion – Summation?
• economics, the environment, culture

83. • We’ve got to get all of these things working
together and the environment can be on the
side of human wellbeing because poor rural
people depend directly on the environment
for their sustenance.
• If they want to have a sustainable sustenance,
they have to have a sustainable environment.

84. • First of all, population studies gives you tools
and analytical perspectives to understand
better the world around you.
• Secondly, it makes you appreciate the culture
of people so you can understand why they
behave in certain manner
• And third, It leads to understanding the
reciprocity of other species to the
improvement of human wellbeing.