02 Population dynmcs-3.pptx

Population dynamics
By: Tadesse N.(MPH/RH, Assistant professor)
April, 2023

Objectives
At the end of the session students will be able to:
List measures of fertility
Calculate fertility and mortality of population
Evaluate measure of mortality, fertility and migration
Identify determinants of Variations in fertility and
mortality
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Introduction
Definition of terms
 Fertility:- the actual reproductive performance of a
population. Production of a live birth or it is the occurrence
of birth
 Fecundity:- physiological (biological) capacity to conceive
(reproductive potential)
 Infecundity (sterility):- lack of the capacity to conceive
 Primary sterility - never able to produce a child
 Secondary sterility - sterility after one or more children
have been born
 Infertility :- Inability to produce a live birth

Definitions…Cont’d
 Fecundability:- Probability that a woman will conceive
during a menstrual cycle. A woman is considered fecund if
she is capable of bearing a live birth, even if she has not
given a birth yet.
 Natural fertility: Fertility in the absence of deliberate parity-
specific control
 Reproductivity: extent to which a group is replacing its own
numbers by natural processes
 Parity: number of children born alive to a woman

Definitions…Cont’d
 Birth interval: time between successive live births
 Pregnancy interval: time between successive pregnancies of a
woman
 Gravidity: number of pregnancies a woman has had whether
or not they produce a live birth
 Live birth: the birth of a child with some symptoms of life (i.e.
movement in the diaphragm, any sort voice, pulse rate )
 Still Birth: the birth of a child with complete disappearance of
life
 Mortality: the complete disappearance of life once a live birth
occurred

Measurements of Fertility
Fertility in the study of demography , refers to the
number of live births a woman has actually had.
measure of reproductive performance of women.
It differs from fecundity, which refers to the physiological
capability of women to reproduce.
 Fertility is directly determined by a number of factors
that, in turn, are affected by a great many social, cultural,
economic, health, and other environmental factors.
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Fertility- importance and issues
Major factor in population dynamics
 Main determinant of population change- Growth in
populations is mainly affected by fertility level
 Affects the age composition/ shape of a population
 Age composition in turn affects fertility
 Affects child and maternal health, and, mortality
 Is also affected by child mortality
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Measuring Fertility Level
Fertility rate: measures the rate at which a population
adds to itself by births.
The Basic fertility indices are
Crude Birth Rate (CBR)
 Child-woman Ratio (CWR)
 General Fertility Rate (GFR)
 Age specific Fertility Rate (ASFRs)
 Total Fertility Rate (TFR)
 Gross Reproduction Rate (GRR)
 Net Reproduction Rate (NRR).
 Marital Fertility
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Measurements of Fertility
1. Crude Birth Rate (CBR) - It is expressed as the number of live
births in a year per thousand of the mid year population.
Mathematically:-
CBR= Bi X 1000
P
Where, CBR is crude birth rate
Bi is total live births during a year.
P is estimated mid year population
 Only live births during the year are taken in to account
 It is not only the simplest but also the most commonly
used measure of human fertility.

Measurements of Fertility…Cont’d
Merits
 CBR requires least information (Only total population &
total live births during a year)
 It provides the rate at which population increases through
birth
Drawbacks
 It uses the total population as a denominator including
large mass of male and female children and older adults
not involved in the process of reproduction
 It does not take in to account the age and sex composition
and marital status of the population under investigation
 Thus, the Crude Birth Rate gives only a general idea about
the fertility and rightly known as crude

2. Child Woman Ratio
 Is expressed as the number of children below five years of age per
thousand females of reproductive age group
 It takes in to account females in the reproductive age group only
Child women ratio = Po - 4 X 1000
Pf 15- 49
Where , Po- 4 is the number of children under five years of age
Pf 15- 49 is the total number of women in the child bearing age
Some draw backs of the Fertility Ratio
 It includes only surviving children below five years of age and not all children
who are actually born
 It takes in to consideration all females in age group 15- 49 years irrespective
of their marital status.
 It can be affected by migration of females. Sometimes females may move to
another place of residence leaving their children behind their native village.

3. General Fertility Rate ( GFR): It is expressed as the number of live
births in a year per thousand women of the reproductive age
group
GFR = _Bi_X 1000
Pf 15- 49
Where; Bi is total number of live births in a year
Pf 15- 49 is the total number of women in their reproductive age
Draw backs
 Child bearing incidence may vary for women aged 15- 49 years.
Because child bearing incidence is higher during 25 - 29 years
than other year.
 It takes in to account all females aged 15 - 49 years irrespective
of their marital status

4. Age Specific Fertility Rate (ASFR)
 Number of live births per 1,000 women of a specific age
(group)
 It measures the total number of live births in a year to
women of a given age group per thousand women in that
age group
Mathematically:- nfx = nBx
nWx
Where; nfx is Age Specific Fertility Rate
 nWx is the total number of women in the age group X to X + n years
 nBx is the total number of live births to a woman in age group X to X+n
years
 X refers to the lower class boundary of the age interval

Age Specific Fertility Rate for Addis Ababa city in 1994 (Table 1)
Age group No of women
(nWx)
No of births
(nBx )
Age Specific Fertility Rates ( nfx)
(nBx)
(nWx)
15 - 19 185,031 1996 0.01
20 - 24 145,093 7679 0.053
25 – 29 108,927 10,389 0.095
30 – 34 68,866 6776 0.094
35 – 39 71,970 4770 0.066
40 – 44 40,626 1142 0.028
45 - 49 31,520 382 0.012
 This type of measure of fertility permits detailed comparison between population and
is helpful in revealing the differences in fertility rates of women belonging to different
age groups. Thus, ASFR is an age - sex adjusted measure of fertility

0
0.05
0.1
0.15
0.2
0.25
0.3
15-19 20-24 25-29 30-34 35-39 40-44 45-49
A
S
F
R
Age group
Age Pattern of Fertility in Ethiopia in
2014
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Advantage of age specific fertility rate
It permits detailed comparison between population
helpful in revealing the differences in fertility rates of
women belonging to different age groups.
Thus, ASFR is an age - sex adjusted measure of fertility
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Measurements of Fertility…
16

5. Total Fertility Rate (TFR): is the average number of children a
woman would have at the end of her reproductive life if she
passes or follows the Age Specific Fertility Rates observed over
a specified time.
 TFR can be obtained by summing up the Age Specific Fertility Rates and
multiplying it by the length of age interval in which the age group is
classified
TFR = n x ∑nfxi
Where; TFR is the Total Fertility Rate
n is the age interval in which the age group is classified
∑nfxi is the sum of Age Specific Fertility Rates

 TFR from the table 1 which shows the ASFR of Addis Ababa city
would be
TFR = 5 x ∑nfxi ( ∑nfxi is 0.358 from table 1). TFR = 5 x 0.358 = 1.79 ≈
2
 This shows that, a woman of Addis Ababa would have two
children at the end of her reproductive life (Age of 50)
Assumptions
 A woman should survive to the end of her reproductive life
 A woman should follow the Age Specific Fertility Rate observed
in a single year

6. Gross Reproduction Rate (GRR)
 GRR is interpreted as the average number of daughters a
woman would have if she survives at least to the age of 50
and experienced FASFR observed in a single year.
 GRR assumes no mortality of daughters until they replace
their mothers

7. Female Age Specific Fertility Rates (FASFR)
 It expressed as the number of female births in a year to
woman of a given age group per thousand women in that
particular age group
■ FASFR = nFBx
nWx
Where, FASFR is female age specific fertility rate
 nFBx is the number of female live births to women aged x
to x+n years
 nWx is the number of women in their reproductive life who
are aged x to x+n years.

Female Age Specific Fertility Rates for Addis Ababa city in 1994
Age group No of women
(nWx)
No of Female
births
(nFBx )
FASFR ( nFBx)
(nFBx)
(nWx)
15 - 19 185,031 969 0.005
20 - 24 145,093 3728 0.026
25 – 29 108,927 5068 0.047
30 – 34 68,866 3338 0.048
35 – 39 71,970 2305 0.034
40 – 44 40,626 560 0.014
45 - 49 31,520 192 0.006

GRR = n x ∑FASFRs
Where, GRR is Gross Reproduction Rate
■ n is the age interval in which the age group is classified
■ ∑FASFRs is the sum of Female Age Specific Fertility Rates
From table 2 ∑FASFRs is 0.178
Thus, GRR = 5 x ∑FASFRs
GRR = 5 x 0.178 = 0.89 ≈ 1
 This shows that the ability of Addis Ababa woman to
reproduce themselves. Or the ability of Addis Ababa
women to replace themselves is about one in 1994

8. Net Reproduction Rate (NRR)
 NRR is the average number of daughters that a woman
would have if she survive to the age of 50 and experienced a
given set of Female Age Specific Fertility Rates through out
her reproductive life with allowance made for mortality of
female births.
NRR is a GRR which is adjusted for mortality of daughters
 The adjustment is performed by multiplying each Female
Age Specific Rates by the probability of surviving from birth
to the age mothers
 So, to calculate the Net Reproduction Rate (NRR), we need
both FASFRs and a life table of survival ratio

NRR= n x ∑(FASFR x SRi)
Where NRR is the net reproduction rate
 n is the age interval in which the age group is classified
 FASFR is Female Age Specific Fertility Rate
 SRi is the survival ratio to the age group
N.B. NRR is thus always slightly less than GRR. The extent of the
difference being depends on the level of mortality of female
births

Marital Fertility
 In many societies child bearing mostly happens for couples
under marital union.
Therefore it is pertinent to focus on measuring fertility of
currently married women
Even in the case where child bearing outside of marriage is
not uncommon – it is useful to measure marital fertility
separately from that of all women.
Marital fertility rates are simply extensions(further
refinement) of the basic fertility rates described for all
women by limiting to currently married women
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Marital Fertility …
Marital fertility rates: important measures includes:
General Marital Fertility Rate- GMFR
Age specific marital fertility rate- ASMFR
Total Marital Fertility Rate- TMFR
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1. General Marital Fertility Rate- GMFR: is defined as the
number of live births occurring to married women in a year
per 1000 married women 15 to 49 years of age at the middle
of the year.
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2. Age specific marital fertility rate- ASMFR: Age-specific marital
fertility rates may also be computed for women in specific age
categories.
• That is,,
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3. Total Marital Fertility Rate(TM): This is usually a measure of
fertility obtained by summing age specific marital fertility
rates of five year-age groups and multiplying by 5. This is
given by the formula:
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Factors affecting fertility
Model of fertility change
Model of reproduction
Bongaart’s Model & Proximate determinants
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Proximate Determinants of Fertility
 Bongaarts (1982) provided an analytical model for measuring in
surveys the most important proximate determinants that affect
fertility
Bongaart’s Proximate Determinants
The 7 proximate determinants are:
1. Proportion of married women among all women of reproductive age
2. Contraceptive use and effectiveness
3. Duration of postpartum infecundability (or postpartum
insusceptibility)
4. Induced abortion
5. Fecundability (including frequency and timing of intercourse)
6. Prevalence of permanent sterility
7. Spontaneous intrauterine mortality

 The following four factors substantially account for the trends
and differentials seen in fertility over time or place
 Proportion of women in sexual unions (Marriage)
 The level of contraceptive use
 Duration of postpartum infecundability
 The level of induced abortion

 The remaining three proximate determinants are relatively
less important determinants of the trends and differentials in
fertility (though sterility due to disease is important in some
SSA regions) . These include:
● The level of permanent sterility
● Frequency of intercourse (fecundability)
● Spontaneous intrauterine mortality

Underlying Determinants of Fertility in
Populations
 The underlying determinants of fertility are those socio-economic,
cultural, health and programmatic factors that result in changes in
reproductive behaviors in populations.
 All underlying determinants must operate through the proximate
determinants to influence the level of fertility in a population.

Underlying Determinants of Fertility in
Populations
 Underlying determinants of Fertility: Some Examples
 Social: education, income, work, status of women
 Cultural: marriage practices, post-partum abstinence, religious beliefs
about contraception
 Health: prevalence of STDs, malaria
 Political: government policies regarding family planning, female
education
 Programmatic: availability of contraceptive information and services

The Bongaarts Model
TFR = TF x Cm x Cc x Ca x Ci
where:
TFR = Total Fertility Rate
TF = Total natural Fertility rate (total fecundity rate)
Cm = index of non-marriage
Cc = index of non-contraception
Ca = index of induced abortion
Ci = index of lactational infecundability
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The Bongaarts Model …
The value of each index ranges between 0 and 1; the lower the
index value, the greater the inhibiting effect of the variable.
Each of these indices can be estimated from survey data to
assess the relative contribution of each of these proximate
determinants to the level of fertility .
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1. Index of Non-Marriage(Cm)
By definition the index of non-marriage is the ratio between
the total fertility rate (TFR) and the total marital fertility rate
(TM). That is:
Cm = TFR/TM
This index (Cm) expresses the effect of non-marriage in terms
of reduction in fertility per woman. OR
The index Cm gives the proportion by which TFR is smaller
than TM as the result of non-marriage;
Cm 0 if nobody is married and Cm 1 if all women are married
during the entire reproductive period.
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2. Index of Contraception(Cc)
To estimate the effect of contraception on marital fertility,
the following equation expresses marital fertility as the
interaction of contraceptive practice and natural fertility:
• TM = Cc x TNM
• where TM- total marital fertility rate;
• TNM = total natural marital fertility rate,
• Cc - index of non contraception.
Equation simply states that TM is smaller than TNM by a
proportion Cc, with the value of Cc depending on the
prevalence of contraception, that is, the extent of use and the
effectiveness of contraception (induced abortion is assumed
absent for the moment).
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When no contraception is practiced, Cc equals 1 and TNM = TM
when all non sterile women in the reproductive years are
protected by 100 percent effective contraception, Cc = 0 and TM
= 0.
The index of contraception is calculated according to the
following formula: {it is shown that, if all couples who practice
contraception are assumed non-sterile, the index Cc can be
estimated as }
Cc = 1 - (1.18 x u x e)
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Where:
u = the overall proportion of married women
currently practicing contraception
e = the weighted average of contraceptive use
effectiveness using the proportions of current
contraceptive users of each method as weights
1.18 is a sterility correction factor
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3. Index of Induced Abortion (Ca)
Computation of the index of induced abortion requires first the
estimation of the age specific induced abortion rates from which one
can calculate the total abortion rate (TA):
The total abortion rate is then used to estimate the total number
of births averted per woman (A) as follows:
A = b x TA
 A = 0.4(1 + u) x TA
where:
 b = births averted per induced abortion;
 0.4 is an estimate of births averted per induced abortion in the absence
of contraception.
 u = the prevalence of contraception
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After the total number of births averted per woman (A) is
estimated, the index of induced abortion is calculated as:
 Ca = TFR/(TFR + A)
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4. Index of Lactational Infecundability (Ci)
The effect of lactational infecundability on fertility operates
entirely through modification of the birth interval.
The ratio of the average birth intervals without and with
lactation will be called the index of lactational infecundability.
The equation to estimate the index of infecundability is as
follows:
Ci = 20.0/(18.5 + i)
where: (18.5 + i) is the average birth interval with lactation
i = average duration of postpartum infecundability
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This equation implies that 20 months is the birth interval in
the absence of lactational infecundability;
allowing 7.5 months as waiting time to conception,
2 months to account for spontaneous fetal wastage,
9 months for term gestation, and
1.5 months for infecundability without lactation.
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The relationship between lactation and the total natural
marital fertility rate, TNM, is summarized by the equation
TNM = Ci x TF
where TF total fecundity rate equal to the total natural
marital fertility rate in the absence of lactation. or
From the above two equations it follows that without
lactation, Ci = 1 and TNM = TF, because i = 1.5 months.
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Estimation of Total Fertility(TFR)
The total fertility rate is estimated from the indices
according to the Bongaarts model:
TFR = 15.3 x Cm x Cc x Ca x Ci
15.3 is an average estimate of TF that Bongaarts has
derived based on data from multiple studies.
It is generally used for this analysis unless there is specific
data from the population under study to derive a better
estimate, which is not usually the case.
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Measures of Mortality
Mortality refers to deaths that occur within a population
(reduction of population).
The incidence of death can reveal much about
The living standard,
The health status of a population and
The availability of health services.
24/10/2023 49

Mortality measures…
1. Crude Death (Mortality) Rate (CDR)
The crude death rate is the number of deaths per 1,000
population in a given year.
CDR = Total number of deaths in a year X 1,000
Mid-year population
Midyear population is an approximation of the average
population exposed to risk
It is obtained from censuses and surveys.
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2. Age specific Death (Mortality) Rates
Number of death per 1000 person of specific age group.
 Death Rates can be calculated for specific age groups, in
order to compare mortality at different ages.
 E.g. for infants (< one year of age), children 1-4 yeas of age,
children under five years, etc.
ASMR = Number of deaths in a specific age group X 1000
Mid-year population of the same age group
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Mortality measures …
3. Infant Mortality Rate (IMR)
Infant Mortality Rate is the number of deaths of infants under one
year of age (0-12 months of age) per 1000 live births in a given
year.
Infant (children under one year of age) are at highest risk of death
than any other age group.
IMR = Number of death of children < 1 year of age in a year X 1000
Total live births during that year
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The infant mortality rate is considered to be a sensitive indicator of the
health status of a community,
Because it reflects the socio-economic condition of the population; i.e.
The level of education,
Environmental sanitation,
Adequate and safe water supply,
Communicable diseases,
Provision of health services etc.
These factors mostly affect infants and children under five years of age.
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4. Child Mortality Rate (CMR)
 It is the number of deaths of children 1-4 years of age per 1000
children 1-4 years of age.
It is also a sensitive indicators of the health status of a community.
CMR = Number of deaths of children 1-4 year of age in a year X 1000
Total number of children 1-4 years of age
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5. Under Five Mortality Rate (<5MR)
It is the number of deaths of children under five years of age in a
year (0-4 years of age) per 1000 children under five years of age (0-
4 year) 59 month.
It is also a very good indicator of the health states of a community.
It can also be calculated as the number of deaths of children under
five years of age in a year per 1000 live births
<5MR = Number of deaths of children <5 yrs in a year X 1000
Total number of children < 5 years of age
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6. Neonatal Mortality Rate (NMR)
Neonatal period is the first month of age of an infant.
Neonatal mortality (death) is the death of infants under one month
(<4 weeks) per 1000 live births.
NNMR = Number of deaths of infants < 1 month in a year X 1000
Total number of live births in the same year
Neonatal mortality rate reflects mortality due to:
Maternal factors during pregnancy
 Birth injuries
Neonatal infection, etc.
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7. Maternal Mortality:- Maternal death is death of a woman while
pregnant or within 42 days of termination of pregnancy, irrespective
of the duration or site of the pregnancy, from any cause related to or
aggravated by the pregnancy or its management but not from
accidental causes (WHO).
Let Dmc = death due to maternal cause.
B= total live birth
Maternal Mortality (Death) Ratio (MMR)
Maternal mortality ratio number of maternal deaths due to maternal cause per
100,000 live births.
MMR = Dmc × 100,000
B
It is a sensitive indicator of health status of a population.
It reflects the socio- economic status of a community.
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8. Maternal mortality rate (MMR)
Number of death due to maternal causes per 1000 women of
reproductive age.
MMR = Dmc × 1,000
W(15-49)
Let Dmc = death due to maternal cause.
W(15-49) = number of woman in reproductive age.
 Note - Maternal Mortality Ratio is most widely used.
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9. Sex Specific Death Rates (SSDR)
Sex Specific Death Rate is the number of deaths among a specific
sex group (males or females) per 1000 population of the same sex
group.
SSDR = Number of deaths among males X 1000
Total number of males
Sex specific mortality rate is used to determine which sex group is
at higher risk of death than the other.
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Life table
The set of probabilities used in estimating the probability of
death or survival at each year and the cumulative probability of
survival to each year is called a life table.
To carry out the calculation, we first set out for each year (X) :
 the number alive at the start = nx
 the number withdrawn during the year=wx
 the number at risk = rx
 the number dying = dx
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Life table calculation for parathyroid cancer survival:
the survival times are given in years after diagnosis
Year
( x )
Number at start
( nx )
Withdrawn
during year
( wx )
At risk
( rx )
Deaths
( dx )
Prob. of death
( qx )
Prob. of surviving
year X
( px )
Cumulative prob. of
surviving x years
( Px )
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
20
17
15
14
14
13
12
9
8
7
5
3
2
2
2
1
1
1
2
2
0
0
1
1
1
0
1
0
2
0
0
0
0
0
0
1
19
16
15
14
13.5
12.5
11.5
9
7.5
7
4
3
2
2
2
1
1
0.5
1
0
1
0
0
0
2
1
0
2
0
1
0
0
1
0
0
0
0.0526
0
0.0667
0
0
0
0.1739
0.1111
0
0.2857
0
0.3333
0
0
0.5000
0
0
0
0.9474
1
0.9333
1
1
1
0.8261
0.8889
1
0.7143
1
0.6667
1
1
0.5000
1
1
1
0.9474
0.9474
0.8842
0.8842
0.8842
0.8842
0.7304
0.6493
0.6493
0.4638
0.4638
0.3092
0.3092
0.3092
0.1546
0.1546
0.1546
0.1546
rx=nx-½wx, qx=dx/rx, px=1-qx, Px=pxPx-1
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Life table…
• In year 1, the number at the start is 20, the number withdrawn is
2, the number at risk, is therefore, r=n1-½w1=20- ½x2 = 19
• the number of deaths in the same year is 1
• As there were 2 withdrawals and 1 death the number at the start
of year 2 is 17.
• For each year we calculate the probability of dying in that year for
patients who have reached the beginning of it, qx=dx/rx and hence
the probability of surviving to the next year, px=1-qx.
• Finally, we calculate the cumulative survival probability.
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Life table…
 For the first year, the probability of surviving the year, P1=p1.
 For the second year, P2=p2P1
That is, the probability of up to the start of the second year,
P1, times the probability of surviving that year (p2).
P3=p3P2 (The probability of surviving for 3 years)
P4=p4P3 (The probability of surviving for 4 years)
From the present life table we can estimate the five year
survival. That is, for the parathyroid cancer, the five year
survival rate is 88%.
What is the estimate for the ten year survival ?
24/10/2023 63

Determinants of Variations in Mortality
Underlying Determinants Mortality
 Socio-economic factors: Household wealth, community
development, women’s education and employment, etc.
 Institutional factors: Health systems, health regulations,
technological developments, information programs,
environmental interventions, etc.
 Cultural factors: Traditional beliefs about health and
disease, religious values, role and status of women etc.
 Broader context: Ecological setting, political economy,
transportation and communication systems, agricultural
development, markets, urbanization, etc.

Migration
Definitions and Measurement
 Migration: Geographic movement of people across a specified
boundary for the purpose of establishing a new permanent or
semi-permanent residence (refugees are not considered as
migrants!).
 Or it is the spatial mobility of individuals from one area (origin)
to another (destination) by crossing boundaries either because
of pull or push factors and/or an amalgam of the two.

Migration
 Migration can be broadly categorized in to two:
1. International Migration - it is migration between and among
countries of the world
 Immigration :move into a new country
 Immigrant: An international migrant who enters the area
from a place outside the country
 Emigration: moving out of home country
 Emigrant: An international migrant departing to another
country by crossing the international boundary

Migration
2. Internal migration: it refers to movement of people within one
country itself
 In-Migration: movement into a new politically
/geographically / administratively defined area within the
same country
 In-Migrant : A person who moves into a new area within the
same country
 Out-Migration : movement out of a
politically/geographically/ administratively defined area
within the same country.
 Out-Migrant: a person who moves out of a area within the
same country

Causes of Migrations
In general we can divide factors causing migrations into two
groups of factors:
Push and pull factors
Push and pull factors are those factors which either forcefully
push people into migration or attract them.
A push factor is forceful, and a factor which relates to the
country from which a person migrates. It is generally some
problem which results in people wanting to migrate.
A pull factor is something concerning the country to which a
person migrates. It is generally a benefit that attracts people to a
certain place.
24/10/2023 68

Push Factors
Not enough jobs
Few opportunities
Political fear
Poor medical care
Not being able to practice
religion
Loss of wealth
Natural Disasters
Death threats
Slavery
Pollution
Poor housing
24/10/2023 69

Pull Factors
Job opportunities
Better living conditions
Political and/or religious freedom
Enjoyment
Education
Better medical care
Security
Family links
24/10/2023 70

Migration…
Migration like any other process shapes many fields of life, having
both advantages and disadvantages.
Effects of migrations are:
Changes in population distribution
Since migration is selective of particular age groups, migrants are mostly
young and in productive age.
It can cause a demographic crisis – what in turn can be followed by economic
problems (shrinking group of economically active population has to finance
extending group of inactive population).
24/10/2023 71

Gross and Net Migration
Gross migration:-is the sum of immigration and emigration or if one is
considering internal migration, the sum of in-migration and out-
migration.
 Net migration:- is the difference between the two flows.
 Internal migration
 Gross=In-migration + Out-migration
 Net=In-migration – Out-migration
International migration
Gross=Immigration + Emigration
Net=Immigration - Emigration
24/10/2023 72

Measurements of Migration
 Immigration Rate : refers to the number of migrants arriving
at a destination per 1000 population at that destination in a
given year.
Number of Immigrants X1000
Total Population at Destination
 Emigration Rate : refers to the number of emigrants departing
an area of origin per 1,000 population at the area of origin in a
given year
Number of Emigrants X1000
Total Population at Origin

Measurements of Migration…Cont,d
 Net Migration Rate : refers to the difference between the
number of immigrants and emigrants, expressed as increase
or decrease per 1,000 population of the area in a given year
Number of immigrants - Number of Emigrants X 1000
Total Population

02 Population dynmcs-3.pptx

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