Comparative Graphical Method of Population Forecasting

Comparative graphical method of population forecasting is a variation of simple graphical method.

Comparative Graphical Method of Population Forecasting

Assumption of Comparative Graphical Method:

“The city taken for consideration will exhibit same population growth as shown by the cities having similar conditions and characteristics.”

Steps for Population Forecasting by Comparative Graphical Method:

1. Different cities are taken which show similar growth characteristics to the city in consideration. Additionally, these cities should have achieved the present population of the city in consideration a decade or two ago.
2. Population curve of these cities are then plotted.
3. An average curve from the population curves of these cities is represented by dotted line.
4. The population curve of the city in consideration is then extended following the pattern of the average population curve.

Advantage & Disadvantage of Comparative Graphical Method

Advantage: Population can be forecasted even if some of the data of past census is not available.

Disadvantage: It is very difficult to find the cities showing the same growth characteristics and have achieved present population of the city in consideration.

Comparative Graphical Method Example

City N shows same growth characteristics as that of A, B, C, and D.

Census data of city A             

Year	1961	1971	1981	1991
Population (in lakhs)	50	62	72	108

Census data of city B

Year	1961	1971	1981	1991
Population (in lakhs)	50	58	69	96

Census data of city C

Year	1961	1971	1981	1991
Population (in lakhs)	50	56	64.5	95

Census data of city D

Year	1961	1971	1981	1991
Population (in lakhs)	50	54	58	102

Census data of city N

Year	1961	1971	1981	1991
Population (in lakhs)	50	56	60	110

Solution:

1. Plot the population curves of city A, B, C, & D. also plot the population curve for the city N.
2. Plot average population curve from the population curves of cities A, B, C, & D.
3. Extend the population curve of city N beyond 110 lakh parallel to the average population curve.
4. Note down the population corresponding to the year 2011 from the extended curve.