Demography population definition morbidity mortility

for nursing 8th semester student

1. BY: SYED BABAR ALI
Demography

2. Outline
By the end of the unit the learners will be able to:
1.Discuss the International health problems including
demographic, health, and epidemiological
transitions.
2.Compare the different phases of natural history of
disease transmission.

3. Demography

Demography comes from two Greek words Demos
meaning people and Graphos meaning to write.
The term was first used by a Belgian statistician,
Achille Guillard, in 1855 in the title of his book
Elements de statistique humaine: Ou demographie
compare (Pressat 1985).

4. Demography
Another dictionary emphasises some of the important
components by defining Demography as ‘the study of human
population in relation to the changes brought about by the
interplay of births, deaths and migration’ (Pressat 1985).
Demography focuses on at least the following five aspects of
human populations:

Size
Distribution
Composition
Components of population change, and
Determinants and consequences of population change

5. Demography
Demographers use census data, surveys, and
statistical models to analyze the size, movement, and
structure of populations.

6. By the beginning of the 21
st
century, world
population reached 6 billion. Most of the growth
has occurred in the past 200 years.

7. Figure World Population Growth
Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Third
edition. Population Reference Bureau 53(3); 1998: 38

8. Doubling time
The unprecedented population growth of modern
times heightens interest in the notion of doubling
time.
Calculation of population doubling time is facilitated
by the Law of 70.

9. Rule of 70
If a population is growing at a constant rate of 1% per
year, it can be expected to double approximately every
70 years
-- if the rate of growth is 2%, then the expected
doubling time is 70/2 or 35 years.

10. Thomas robert malthus, was the first
person to draw widespread attention
to the two components of natural
increase, births and deaths (fertility
and mortality).
T.R. Malthus, 1766-
1834

11. In his Essay on the Principle of
Population, initially published in
1798, Malthus postulated that
population tended to grow
geometrically while the means of
subsistence (food) grew only
arithmetically.

12. The Malthusian Trap
arithmetic growth (food):
1, 2, 3, 4, 5, 6, 7, 8, 9, 10…
geometric growth (population):
1, 2, 4, 8, 16, 32, 64, 128, 256, 512…

13. Malthus argued that the difference between
geometric and arithmetic growth caused a
tension between the growth of population
and that of the means of subsistence.
-- this gap could not persist indefinitely.

14. Owing to war, disease, hunger, and vice,
mortality would serve as a positive check
on population growth.

15. Preventive checks: birth control through
(1) later age at marriage.
(2) Abstinence from sex
(Malthus opposed artificial methods of birth control on
moral grounds. Viewed contraception as a vice)
Solution to the Malthusian Trap

16. Contrary to Malthus's prediction, mortality has not yet risen to
curb world population growth.
< 1 billion people in 1800
6 billion by the end of the
20
th
century
Population Explosion

17. Why was Malthus unable to foresee the population
explosion (also known as the population bomb)?
He did not recognize the force of the industrial revolution,
which produced exponential growth in the means of
subsistence.
Population Explosion

18. During the first half of the 20
th
century,
demographers conceived the notion of
the demographic transition.
The Demographic Transition

19. The demographic transition
framework illustrates population
growth in terms of discrepancies and
changes in two crude vital rates –
mortality and fertility (ignores
migration)
The Demographic Transition

20. CRUDE DEATH RATE (CDR) =
# DEATHS IN CALENDAR YEAR
*
K
MID–YEAR POPULATION
CRUDE VITAL RATES

21. CRUDE BIRTH RATE (CBR) =
# BIRTHS IN CALENDAR YEAR
* K
MID–YEAR POPULATION
RATE OF NATURAL INCREASE =
CBR - CDR
CRUDE VITAL RATES

22. Figure 2 The Demographic Transition
Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Third edition.
Population Reference Bureau 53(3); 1998: 39

23. Fig Demographic/ Epidemiologic Transition Framework
Source: Ian R.H. Rockett. Population and Health: An Introduction to
Epidemiology. Second edition. Population Reference Bureau 54(4); 1999: 9

24. 24
The Demographic Transition Theory …
Stage I
Both birth and death rates are high with the two rates
being approximately equal
Population growth is slow, although the potential for
more rapid growth exists
The death rate fluctuates in response to war and disease
This stage involves a low-income agricultural economy

25. 25
The Demographic Transition Theory …
Stage II
Dramatic reduction in death rate as a result of
industrialization and related medical and health
advances
This reduction in death rate is not accompanied by a
parallel reduction in birth rate
Hence, the rate of natural increase (r) is high
Population growth is rapid

26. 26
The Demographic Transition Theory …
Stage III
Declining birth rate, the result of voluntary decisions to
reduce family size facilitated by advances in
contraceptive techniques
This is related to increased standards of living
r falls as birth rate approaches the already low death
rate
Population growth is once again slow

27. 27
The Demographic Transition Theory …
Stage IV
 Birth and death rates are again, as in the first stage
approximately equal
A low r reappears
The transition involves a change in high birth rate and
death rates to a much more socially acceptable state of
affairs

28. 28
The Demographic Transition Theory …
Developed vs. Developing Nations
All industrialized nations have gone through these stages of
demographic transition
The developing nations have completed Stage I and are currently
in stage II - a phase of explosive rates of natural increase
While these countries will eventually complete their
demographic transitions, what is uncertain is how long this
process will take
Countries in western Europe took roughly 200 years to complete
their transitions
But the less developed regions of the world can not wait to so
long if social upheaval and environmental disaster on a global
scale are to be avoided

29. Summary