Planning Techniques

Population projection | Meaning, Importance and Need

What is population projection?

Population projection deals with computations of future projection size and characteristics based on assumptions about future trends in fertility, mortality and migration.  Since it is not possible to predict the future trends in fertility, mortality and migration with cent percent certainty, it is also not possible to predict the future size and characteristics of a population accurately. Projections are merely intelligent exercise as to what would happen to current population under specified assumptions of fertility, mortality and migration in future years. Town Planning requires a fair idea of future for which planning needs to be done. For this purpose planners use various methods and tools for “predicting” the future which generally involves population data and population projection as people are the ones who need to be kept in mind and they are the ones for whom planning is done.

This is perhaps the single most important population study for planning purposes. Many important factors of the future situation facing the community on which the planner must advise are derived directly from the population projection. It forms a framework for a great deal of the subsequent work in devising, testing, evaluating and implementing the plan. Most of the important decisions about major land uses and services are derived from population estimates: the demand for water, power and waste disposal facilities; housing, open spaces and schools; the supply of labor; spending power available for the retail trade, the numbers of private cars to be, etc. One must realize that a projection of great sophistication will eventually be used to derive land areas by the application of a standard and that the accuracy or relevance of the standard may be far more important than great refinement in the population projection. Also, one should recall that the cyclical nature of planning, involving regular reviews, gives the opportunity to revise and improve the population projection as part and parcel of that process.

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Projections are an extrapolation of historical data (population versus time) into the future. The accuracy of population projections is generally considered directly proportional to the size of the existing population and the historical rate of growth, and inversely proportional to the length of the time projection. In other words:

More confidence in projection

  • Short time into the future
  • Large population
  • Historically high growth

Less confidence in projection

  • Long time into the future
  • Small population
  • Historically low growth
population projection
Population projection for an area

Important uses of population projection:

  • Development Planning like housing, employment etc.
  • Projection of labor force for estimating the future production of goods and services.
  • Population Projections by age for requirement of future school enrolments. This will enable planning of investments in school buildings, teacher training and production of educational material.
  • Future demand for food, power, water, transport etc.
  • Projections of the future age and sex composition of the population are essential for estimating the incidence and prevalence of various diseases and planning for the number of hospitals, hospital beds and specialized facilities as well as training programmes for medical specialists.
  • Future consumption requirement of various goods and services by the population can be obtained from the projection of population by age and sex, in different socio-economic strata. For example, the future demand of feeding bottle for children will depend on the projected number of children in future.

Difference between population projection & population forecast:

Forecast has an element of prediction into the near future using current data and sophisticated instruments. Population projection on the other hand, are usually carried out based on a number of alternative assumptions based on trends of growth and other linked factors like future policy of the government, attitude of people etc.

A forecast is based upon assumptions reflecting the conditions the business expects to exist and the course of action reasonably expected to be followed.   A forecast can utilize a specific monetary amount or a reasonable range based on the various assumptions in place.

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Methods of Population Projection

There are number of methods used for projecting the population figures. Different methods are used depending on the need and nature of area for which projection is made. At times, to get better and more accurate figures combination of 2 or more methods may also be adopted. This helps in verifying the population numbers and thus providing a more accurate population projection. Some of the well known and widely used population projection methods include:

  1. Mathematical & Graphical Methods
    1. Linear growth
    2. Exponential growth
    3. Decreasing growth
    4. Correlation method
    5. Component method
  2. The Employment Method
  3. Ratio Methods
  4. The Migration and Natural Increase Method
  5. The Cohort- Survival Method
  6. Matrix Methods

Read in detail about Population Projection Methods

Read about: Delineation of Formal Region, Delineation of Functional Region, National Urban Information System (NUIS)

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