Methods of Population Forecasting for Urban Development
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P
P
OPULATION
OPULATION
F
F
ORECASTING
ORECASTING
M
M
ETHODS
ETHODS
Lecture 3
Eng.Isra’a Al-Smadi
POPULATION FORECASTING
Design of water supply and sanitation scheme is based on the
projected population of a particular city, estimated for the
design period.
Any
underestimated
value will make system inadequate for
the purpose intended;
Overestimated
value will make it costly. Change in the
population of the city over the years occurs,
The system should be designed taking into account of the
population at the end of the design period.
POPULATION FORECASTING
Factors affecting changes in population are:
increase due to births
decrease due to deaths
increase/ decrease due to migration
increase due to annexation
POPULATION FORECASTING
h
t
t
p
s
:
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o
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o
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j
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a
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POPULATION FORECASTING
GROWTH
RATE
%
h
t
t
p
s
:
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P
OPULATION
F
ORECASTING
M
ETHODS
•
The present and past population record for the city can be
obtained from the census population records. After collecting
these population figures, the population at the end of design
period is predicted using various methods as suitable for that city
considering the growth pattern followed by the city
Arithmetic Increase Method
This method is based on the assumption that the
population increases
at a constant rate
; i.e. dP/dt=constant=k;
Where,
P
t
: the population after
t
years
P
0
: present population
k
a
: Constant population growth (unit: capita/year)
P
1
and P
2
Populations in year T
1
and T
2
This method is most applicable to large and established cities
.
E
XAMPLE
1:
if the current population in a city is 40,000 what is the
predicted population after
nine
years if the population
increase
6000
in the last
five
years.
E
XAMPLE
2:
P
P
OPULATION
OPULATION
F
F
ORECASTING
ORECASTING
M
M
ETHODS
ETHODS
Lecture 4
Eng.Isra’a Al-Smadi
Geometric Increase Method
This method is based on the assumption that
percentage
growth
rate is constant
where,
P
o
:the present population,
P
n
:the population (predicted) after 'n' number of decades,
n :number of decades between P
o
and P
n
and,
I
G
:Geometrical growth rate mean (%)
•
growth rate
Geometric Increase Method
This method must be used with caution, for
when applied it may
produce too large results
for rapidly grown cities in comparatively
short time.
This would apply to cities with unlimited scope of
expansion.
As cities grow large
, there is a tendency to
decrease
in the rate of
growth.
E
XAMPLE
3:
E
XAMPLE
3
CONT
…
Incremental Increase Method
This method is
modification of arithmetical increase method
and it
is suitable for an
average size
town under
normal condition
where
the growth rate is found to be in increasing order. While adopting
this method the increase in increment is considered for calculating
future population.
Incremental Increase Method
The incremental increase is determined for each decade from
the past population and the average value is added to the
present population along with the average rate of increase.
Hence, population after nth decade is
Where,
P
n
: Population after nth decade
X : Average increase
Y : Incremental increase
n :number of decades between P
o
and P
n
E
XAMPLE
4:
E
XAMPLE
4
CONT
… :
P
P
OPULATION
OPULATION
F
F
ORECASTING
ORECASTING
M
M
ETHODS
ETHODS
Lecture 5
Eng.Isra’a Al-Smadi
Simple Graphical Method
In this method, a graph is plotted from the available data,
between
time and population
. The curve is then smoothly
extended up
to
the desired year.
This method gives very
approximate
results and should be used
along with other forecasting methods.
Simple Graphical Method
Logistic Curve Method
The three factors responsible for changes in population are :
•
Births
•
Deaths
•
Migrations
•
Logistic curve method is based on the hypothesis that when these
varying influences do not produce extraordinary changes, the
population would probably follow the growth curve characteristics
of living things within limited space and with limited economic
opportunity.
•
The curve is S-shaped and is known as logistic curve.
L
o
g
i
s
t
i
c
(
S
-
s
h
a
p
e
d
)
C
u
r
v
e
Designing water supply and sanitation schemes for cities requires accurate population forecasting. Factors influencing population changes include births, deaths, migration, and annexation. Various methods like Arithmetic Increase, Geometric Increase, and Ratio Method are used to predict population growth for urban planning purposes. The Arithmetic Increase Method assumes constant population growth rate and is suitable for large cities.
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Presentation Transcript
POPULATION FORECASTING METHODS Lecture 3 Eng.Isra a Al-Smadi
POPULATION FORECASTING Design of water supply and sanitation scheme is based on the projected population of a particular city, estimated for the design period. Any underestimated value will make system inadequate for the purpose intended; Overestimated value will make it costly. Change in the population of the city over the years occurs, The system should be designed taking into account of the population at the end of the design period.
POPULATION FORECASTING Factors affecting changes in population are: increase due to births decrease due to deaths increase/ decrease due to migration increase due to annexation
POPULATION FORECASTING https://www.worldometers.info/world-population/jordan-population/
POPULATION FORECASTING GROWTHRATE % https://www.worldometers.info/world-population/jordan-population/
POPULATION FORECASTING METHODS The present and past population record for the city can be obtained from the census population records. After collecting these population figures, the population at the end of design period is predicted using various methods as suitable for that city considering the growth pattern followed by the city Arithmetic Increase Method Simple Graphical Method Geometric Increase Method o Comparative Graphical Method Incremental Increase Method o Ratio Method o Decreasing Rate of Growth Logistic Curve Method Method
Arithmetic Increase Method This method is based on the assumption that the population increases at a constant rate; i.e. dP/dt=constant=k; Where, Pt : the population after t years P0 : present population ka : Constant population growth (unit: capita/year) P1 and P 2 Populations in year T1 and T2 This method is most applicable to large and established cities.
EXAMPLE 1: if the current population in a city is 40,000 what is the predicted population after nine years if the population increase 6000 in the last five years.
POPULATION FORECASTING METHODS Lecture 4 Eng.Isra a Al-Smadi
Geometric Increase Method This method is based on the assumption that percentage growth rate is constant where, Po :the present population, Pn :the population (predicted) after 'n' number of decades, n :number of decades between Po and Pn and, IG :Geometrical growth rate mean (%) growth rate
Geometric Increase Method This method must be used with caution, for when applied it may produce too large results for rapidly grown cities in comparatively short time. This would apply to cities with unlimited scope of expansion. As cities grow large, there is a tendency to decrease in the rate of growth.
Incremental Increase Method This method is modification of arithmetical increase method and it is suitable for an average size town under normal condition where the growth rate is found to be in increasing order. While adopting this method the increase in increment is considered for calculating future population.
Incremental Increase Method The incremental increase is determined for each decade from the past population and the average value is added to the present population along with the average rate of increase. Hence, population after nth decade is Where, Pn: Population after nth decade X : Average increase Y : Incremental increase n :number of decades between Po and Pn
POPULATION FORECASTING METHODS Lecture 5 Eng.Isra a Al-Smadi
Simple Graphical Method In this method, a graph is plotted from the available data, between time and population. The curve is then smoothly extended up to the desired year. This method gives very approximate results and should be used along with other forecasting methods.
Logistic Curve Method The three factors responsible for changes in population are : Births Deaths Migrations Logistic curve method is based on the hypothesis that when these varying influences do not produce extraordinary changes, the population would probably follow the growth curve characteristics of living things within limited space and with limited economic opportunity. The curve is S-shaped and is known as logistic curve.
