The various methods generally adopted for estimating future population.

**I) Arithmetic Increase method**
In this method it is assume that the population increase at a constant rate i.e., the rate of change of population with time is constant.

Pn = Po + n x’

Where,

Pn = population after nth decade

Po = present population

```
n = no. of decades
i = Growth rate of population per decade.
```

**2) Geometrical Increase Method**

In this method, it is assumed that rate of growth is proportional to the increase in population.

Pn=Po(1+i/100)^n

Where,

Pn = Population after nth decade

Po = Present population

N = no. of decades

i = Growth rate per decade.

For the region having unlimited growth this method gives accurate results.

**3) Incremental Increase method**

This method gives almost accurate results because for the future decades the addition is made at an average rate for two consecutive decades. The equation used for the calculation is as below

Pn=Po+nx^'+n(n+1)/2.y^n

Where,

Pn= Population after nth decade

Po= Present population

X’= Aug increase of population of known decades.

Y’= Aug of incremental increase of the known decades.

**4) Logistic Method**

- If the mathematical calculations are plotted on a logistic paper of the population data, we get the logistic curve.
- If growth rate remain constant for all the decade , it appear to be straight line.
- If the straight line is not obtained then the hypothesis of the population growth is not valid.

**5) Ratio Method**

It is very general & crude method to calculate the population of a given region.

By comparing two cities having almost similar sizes and geographical conditions, will help to project the population of another city

**6) Curvilinear Method**

If the population growth of a region is plotted on a graph, it can be extended with the same rate to project the future decade population.

In all the methods the trend of population can be shown & not the accurate figure because the variables are more than the constant i .e the physical environment is constant but the economic, social, cultural , political environmental are varied.