To design a structure, forecasting population is required.
The population of a particular area is increasing gradually. The cause of this increment may be
- Development of new industries
If there are new big industries developed in an area, then population of that area is increased. Because people will migrate towards the industrial area to find the income sources.
- Natural disasters
Natural disasters such as earthquake or flood in adjoining area may cause the population increase in particular area. Because people will move towards the area where there is no flood.
- Educational facilities
Increase in educational facilities in an area may cause poplulation growth in that area.
Other reasons are
- Increase in transport facilities
- Political changes in adjoining countries
Factors that decrease the population may be deaths or migration from the city.
As increase in population is more than the decrease in population. So there is net increase in population.
Methods of forecasting population
There are two methods use to forecast population
- Mathematical methods
- Curvilinear/Graphical methods
There are two mathematical methods to forecast population.
- Arithmetic method
This method is based on the hypothesis that the rate of population growth is constant. This method of forecasting population is used in those cities where population is more or less established.
It can be expressed as
Rate of population growth = constant
- Geometric method
Geometric method of forecasting population is based on the hypothesis that the rate of growth of a particular area is proportional to the population.
This method is used for the region where population is growing rapidly.
Curvilinear or graphical methods
These methods of forecasting population involve the graphical projection of the past population growth curve.
The commonly used graphical methods are
- Using population of the city under growth
In this method the procedure is as follows.
- Plot the population data such as time in years in x-axis and population data on y-axis.
- Join all the points and make the curve of the given data considering various factors.
- Extend the curve considering various factors and find out the population at required future year,
- If the curve is properly extended keeping all the factors in view, this method may result better than that of mathematical methods.
- By constant weight growth fall number
According to this method, the future population can be estimated as
Future population = Present population ( 1 + ϒ )n
ϒ = percentage of growth rate
n= number of years
- By ratio method
It is based on the hypothesis that the population of a city has a relationship to the population of the whole country. The change rate of population of the city is the same as that of the country.
- Comparison with other similar cities
In this method care should be taken that the cities selected for comparison should be as similar as possible to the city under consideration. The cities selected for comparison should have already attained the expected future population of the city.