POPULATION FORECASTING - Logistic CURVE METHOD

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POPULATION FORECASTING - Logistic CURVE METHOD. GROUP MEMBERS. Kush Poorunsing Aman Sahadeo Arshaad Jeedaran Nevin Sunassee Pamben Moonsamy Kishan Joorawon. Population Forecasting. Important process in the design of waste water treatment plants

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Presentation Transcript
GROUP MEMBERS

Kush Poorunsing

NevinSunassee

PambenMoonsamy

KishanJoorawon

Population Forecasting
• Important process in the design of waste water treatment plants
• Factors affecting change in population:
• Fertility/ Birth rate
• Death rate
• Migration
Logistic Method

Saturation population

• Follows some logical mathematical relationship.
• has an S-shape combining a geometric rate of growth at low population with a declining growth rate as the population approaches some limiting value.
Equation - 1
• ………………. (1)
• Where

Pt: population at some time in the future

Psat: population at saturation level

t: number of years after base year

a, b: data constants

Equation - 2
• ……………….. (2)
• Where

Psat: population at saturation level

Po: base population

P1, P2: population at time periods

Equation - 3
• …………………. (3)
• ………………(4)
• Where

n: time interval between successive censuses

Example
• The data for population censuses from 1851 to 2000 for Island of Rodrigues is given below. Estimate the expected population in 2011.
STEP 1
• Three successive years, represented by to, t1, and t2are chosen such that they are equidistant from each other.

t0

t1

t2

STEP 2
• The number of years from toto t1and t1 to t2 is denoted by n.

t0

n=28

t1

n=28

t2

STEP 3
• The population figures corresponding to to, t1, and t2are Po, P1and P2respectivelythrough which the logistic curve is to pass.

t0

P0

n=28

t1

P1

n=28

P2

t2

CALCULATIONS - 1
• n=28
• P0= 11885, P1= 24769 and P2= 35779
• From equation 2,
CALCULATIONS - 2
• From equation 3,
• From equation 4,
CALCULATIONS - 3
• Replacing the values obtained in equation 1, the expected population for 2011 is:
• = 2011-1944 = 67 years
CONCLUSION
• Based on census reports, the population of Rodrigues in 2011 was 37,922 (Wikipedia)
• Estimated population with logistic method is 38420.8
• 1.31% deviation from actual value