Population distribution
By Marjorie Henry, Contributor

Students of Edith Dalton James High School getting wild at the NO Violence in Schools concert. - Ian Allen/Staff Photographer

Population distribution In the previous lesson, I started to review population and settlement, one of the two topics in section three of the syllabus, that is, human systems. The lesson ended with definitions of some demographic terms namely, population distribution and population density. I also looked at the factors that bring about population growth - births, deaths and migration. As I continue with the topic today, I would like, first of all, to refer to the techniques used to represent population distribution and population density.

Population distribution is shown on a statistical map called a dot map. The dots used on the map are quantitative symbols, each having a specific and fixed value. It is therefore possible to count the number of dots on the map, and then multiplying by the dot value, to calculate the total population. The dot map can give a clear visual impression of the differences in distribution, contrasting, as far as possible, areas of greater concentration with areas of a sparser or more scattered nature.

Simple exercise

Let me deviate a bit and give you a simple exercise. Look at the following diagrams and then answer the questions following.

One dot equals five persons

1. Which diagram shows a greater concentration of people?

2. Which diagram shows a sparse population?

3. How many persons are living in Area A?

Your correct answers are 1. - B; 2. - A; 3. - 40. In the event that you did not understand how to do the third question, let me explain. There are eight dots in that area. Each dot represents five persons. Hence, 8 x 5 = 40 persons.

I also mentioned in the lesson last week, the formula to calculate population density, namely

Let's find out the population density of Area A. We are assuming that the size of the area is 4km squared.

Area A = 4km squared

Population = 8 x 5 = 40 persons

Density of population = 40/4 = 10 persons per km squared

Let us also assume that Area B is the same size as Area A. Calculate the population density of Area B. Which area has a higher population density? Now check your answers.

1. The population density of Area B is 30 persons per km squared.

2. Area B has the higher population density.

The statistical map used to represent population density is the choropleth map (or shading map). This map shows the average distribution of the population within an administrative unit, for example, a parish, in the case of Jamaica. The shading becomes denser as there is an increase in the distributional values. Look in your textbooks for examples of choropleth maps. Try to interpret them.

Population growth, the third demographic term mentioned in the previous lesson, is affected by births, deaths and migration. Migration relates to the number of persons entering the country to live permanently (immigration) and the number of persons leaving the country permanently (emigration). Natural increase is what is needed from the data on births and deaths. To obtain this information, the number of deaths is subtracted from the number of births. Add to the number for natural increase, the number from migration, to arrive at the total population increase for the year.

In reference to the data provided by Mark Wilson in his text The Caribbean Environment, we can be informed about the growth of the population in Jamaica, in 1994. At the start of that year the population was 2,482,900. Over the year, there were 59,200 births and 13, 500 deaths. The natural increase was therefore 45,700. The number of persons leaving the island permanently (emigrants) was greater than those who came to live permanently (immigrants). The net migration was -18,800. The net population increase was 26, 900. At the end of the year, the population was 2,509,800.

Assignment

Here is an exercise for you to calculate population growth.

At the beginning of the year, the city of George's Gap has a total population of 10,000,000. There is no migration. The birth rate is 20 per 1000 and the death rate is 15 per 1000. What will be the increase in total population in George's Gap?

In the next lesson, I will discuss information on the factors that influence population distribution.

Remember to keep reading on the topic.

Marjorie Henry is a vice-principal at Glenmuir High School and is head of the Geography Department. She teaches the subject at the CSEC Level.