11 Important Terms Used in the Calculation of Human Population

The Main Factors which are responsible for the Rise in World Populations are:

1. Population Characteristic and Variation among Nations:

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Human population is defined as a group of human being those are living together in a certain space of a country.

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Population characteristic is defining as qualities and characterisation of various types of populations within a social or geographic group, with emphasis on demography, health status, and socioeconomic factors. The main population characteristics are:

2. Exponential Growth:

Population grows geometrically (1, 2, 4, 8 …), rather than arithmetically (1, 2, 3, 4 …), which is why the numbers can increase so quickly. When a quantity increases by a fixed percentage is known as exponential growth e.g., 10,102,103,104……………………… Or 3, 6, 12, 24 etc.

Population growth takes place exponentially and that explains the dramatic increase in global population in the last 150 years. In India the population growth rate is 1.38% where as birth rate and death rate is 22.01 births/1,000 population and 8.18 deaths/1,000 population respectively.

3. Doubling Time:

The number of years required for the population of an area to double its present size, given the current rate of population growth. Population doubling time is useful to demonstrate the long-term effect of a growth rate, but should not be used to project population size. Many more developed countries have very low growth rates and as a result, the equation shows doubling times of hundreds or thousands of years.


But these countries are not expected to ever double again. Most, in fact, likely have population declines in their short doubling times, but are expected to grow more slowly as birth rates are expected to continue to decline.

The growth rate can be used to determine a country or region or even the planet’s “doubling time,” which tells us how long it will take for a country’s current population to double. Many less developed countries have high growth rates that are associated with is determined by dividing the growth rate into 70. The number 70 comes from the natural log of 2, which is .70.

Td = 70 / r where Td = the doubling time in years and r = the annual % growth rate.

4. Total Fertility Rate (TFR):

Total Fertility Rate (TFR) is the average number of children each woman would have in her life time, assuming that current age-specific birth rates remain constant throughout her child bearing years. In a population with equal amounts of in and out migration, a total fertility rate of 2.1 or less can achieve zero population growth in about two generations.


The current total fertility rate worldwide is 2.9. In the more developed countries (with 30 percent of the world population) the current TFR is 1.6 and in the less developed countries (70 percent) the current TFR is 3.3. In India TFR is 2.73 children born/woman (2006 est.).

5. Infant Mortality Rate:

Infant Mortality Rate (IMR) is the number of infants age 0 to 12 months who die per 1000 live births in a given population. On the scale of good to bad, infant mortality rates range from a current low in Japan of 4 to a high of 153 in Guinea.

By 1993 the IMR in Kerala had dropped to 13. Infants 0 to 12 months are most sensitive to the provision of clean water, good food, suitable housing and clothing, quality health care, the education of their parents, and close attention—essential needs of all humans.

Infant mortality rate provides a quick measure of the quality of the food and water available, the quality of housing and clothing, the quality of the health care, and the quality of the education in a whole population. For India the IMR data are available here:

Total IMR: 54.63 deaths/1,000 live births

Male IMR: 55.18 deaths/1,000 live births

Female IMR: 54.05 deaths/1,000 live births (2006 est.)

6. Age Structure:

Age structure of population of a nation can be represented by age pyramids based upon people belonging to different age classes. The reproductive status of the population depends on proportion of individuals of pre-reproductive (0-14 yr), reproductive (15-44 yr) and post reproductive (45 yr and above) stages.

In a rapidly growing population with a high birth rate, each successive generation will be more numerous and there will be more young organisms in the population. In another population the birth rate may be very slow and thus pre-productive age group reduced in proportion to the re-productive and post reproductive groups. If these data are plotted, three types of age pyramids are formed. These are:

i. Expanding Age Pyramid:

Since more individuals of pre-reproductive and reproductive ages than of the post-reproductive age are found in an expanding population, the age pyramid is triangular in shape. Example- India, Nigeria, etc.


0-14 years: 30.8% (male 173,478,760/female 163,852,827)

15-64 years: 64.3% (male 363,876,219/female 340,181,764)

65 years and over: 4.9% (male 27,258,020/female 26,704,405)

ii. Stable Age Pyramid:

The stable age pyramid is bell-shaped, because the proportion of different age groups is more or less the same. Example—France, USA, etc.


0-14 years: 20.4% (male 31,095,847/female 29,715,872)

15-64 years: 67.2% (male 100,022,845/female 100,413,484)

65 years and over: 12.5% (male 15,542,288/female 21,653,879)

iii. Diminishing Age Pyramid:

The age pyramid of the diminishing population is urn- shaped because the proportion of the post-reproductive age group is less than that of the others. Example—Germany, Japan, etc.


0-14 years: 14.2% (male 9,309,524/female 8,849,476)

15-64 years: 65.7% (male 42,158,122/female 41,611,754)

65 years and over: 20% (male 10,762,585/female 14,772,150 [2006 est.]

7. Replacement Level:

Replacement level is the level of fertility at which a couple has only enough children to replace themselves, or about two children per couple but due to infant mortality rate this replacement level is usually changed.

In developed countries with low child mortality, replacement level is below approximately 2.1 children per woman’s life time. 2.1 children per woman includes 2 children to replace the parents, with one-tenth of a child extra to make up for the mortality of children who do not reach the age of 15, which is the defined age when the fertility rate is calculated. For developing country the replacement level is 2.7.

8. Zero Population Growth (ZPG):

Zero Population Growth (ZPG) is the absence of population growth in which equal birth and death rates create a stable human population.

9. Life Expectancy:

Life expectancy is the average number of years remaining for a living being (or the average for a class of living beings) of a given age to live. Life expectancy is also called average life span or mean life span, in distinction to maximum life span. Life expectancy is also defined as the age at which 1/2 of age cohorts have died.

It is the average age that a new born infant is expected to attain in a given country. The average life expectancy, over the globe, has raise by 40-65.5 in last 50 years. For developing country that is 60-65 yr and for developed countries that is 80-85 years. In India, the life expectancy of total population is 64.71 years whereas for male and female is 63.9 years and 65.57 years respectively.

10. Male-Female Ratio:

This is the number of male to the number of female present in a particular area of any country. Due to female infanticides and gender based abortion the ratio has upset in many countries.

CountrySex ratio (male(s)/female)
Germanyunder 15 years: 1.05 male(s)/female

15-64 years: 1.04 male(s)/female

65 years and over: 0.7 male(s)/female

total population: 0.96 male(s)/female
Indiaunder 15 years: 1.06 male(s)/female

15-64 years: 1.07 male(s)/female

65 years and over: 1.02 male(s)/female

total population: 1.06 male(s)/female
Japanunder 15 years: 1.05 male(s)/female

15-64 years: 1.01 male(s)/female

65 years and over: 0.73 male(s)/female

total population: 0.95 male(s)/female
United Statesunder 15 years: 1.05 male(s)/female

15-64 years: 1 male(s)/female

65 years and over: 0.72 male(s)/female

total population: 0.97 male(s)/female

11. Demographic Transition:

The term demographic transition is used to describe the development from high birth rates and death rates to low birth and death rates that occurs as part of the economic development of a country. Usually it is described through the “Demographic Transition Model” that describes the population changes over time.

Population growth is usually related to economic development. There occurs a typical fall in death rates and birth rates due to improved living condition leading to low population growth. The different phases include:

i. Pre-industrial phase, which have high birth rate as well as high death rate.

ii. Transition phase, which have high birth rate but controlled death rate.

iii. Industrial phase, which have controlled birth rate as well as controlled death rate.

iv. Post-industrial phase, in which the country attain zero population growth.


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