Demographic Components, Processes and Measures

 Introduction to Demography

Demography is the study of the human population in a scientific and systematic manner . The study of population and its characteristics is the prime content of demography. Population is never static. It is continuously changing. It increases or decreases because of three demographic components:  birth, death and migration. There are various characteristics of population . We need a systematic study of these characteristics to know and analyze the present, past and future status of population. In order to make it feasible and easy, we study demography. John Graunt of Great Britain is called the 'Father of Demography'  because he studied population data for the first time in the world . He had collected population data from different churches that were related to mortality in England. In1662 A.D , he published a book 'Natural and  political Observation made upon the Bills of Mortality'. People started studying about population trends and their characteristics from the time of Graunt, and an important milestone was made by Achille Guillard in 1855 A.D. Guillard was the first person to coin the term 'demography' in population studies. He wrote a book 'Comparative Demography' in 1855 A.D that brought a new, scientific and statistical concept in studying population in the modern world .

The word  'demography' is composed of two Greek terms 'demos' and 'graphien'.  'Demos' means people and 'graphien' means scientific study. Thus, demography means the scientific study of human population. Only this etymological meaning may not be sufficient to understand the wider scopes of demography. In a broader sense, Demography is defined as  the scientific and statistical study of human populations mainly about their distribution, size ,  composition as well as the causes and consequences of changes in these characteristics.

According to the demographic dictionary published by UNO , 'Demography is the scientific study of human population primarily with respect to their size,  structure , and development.' Population is affected by some specific factors . They are called  demographic components and processes. The effects are statistically analyzed with demographic measures . It is very essential to study these aspects of population to understand the population characteristics and also to formulate the plans and policies for people.

Types of demography 

Formal Demography 

In the traditional and narrow concept of demography, formal demography is the study of human populations related to the basic aspects of human population like size and distribution. UN Multilingual Demographic Dictionary has also focused on such basic aspects of human population under the study of demography. Thus, demography is defined as the scientific and statistical study of human populations mainly about their distribution, size, composition, as well as the causes and consequences of changes in these characteristics. 

Social Demography 

It is the broader and new technique of studying human population in relation to the existing social traits and factors. Demography is directly related to the social traits and characteristics like social traditions, customs, economy etc. Therefore, demography should be studied in the light of such social features and characteristics. Social demography is defined by the Encyclopedia Britannica as the scientific study of people's age, education, residence, socioeconomic and marital status. According to Shyrock and Siegel, "demography is not merely related not only with the population and the determinants of population and changes, it also studies the interrelationships between the other affective factors like social, economic, political, geographical, environmental, biological aspects of the society." Thus, the concept of social demography studies the total situation of population in wider sense. 

Demographic Components 

Birth , death and migration which are responsible for population change are called demographic components  . Population changes are brought by various other factors too, but all these factors bring changes in these components first to do so. Diseases, epidemics , calamities , wars ,etc. increase the death component and decrease the population. Illiteracy, superstition , preference to son, etc. increase the birth component and increase population. Fertility of land, better environment, employment opportunities and various services and facilities attract the people from other  places and bring changes in migration component, which increase the population of the place of destination and decrease the population of the place of origin.

Demographic Processes

The processes of fertility, mortality and migration that bring changes in the demographic components and population composition are called demographic processes. It is the process by which there is a change in the demographic components with the influence of factors affecting the population.

Fertility and fecundity both are related to the birth component. Fecundity refers to the biological capacity of a female to give birth. Fecundity starts in females after menarche or the first menstruation, and it lasts up to menopause, or the last menstruation of her life. The fertile periods of  women is generally considered as the period of 15-49 age groups. Few women have defect in their reproductive functions in their body and cannot produce children. Such women are called infecund or sterile. Fertility is defined as the actual reproductive performance of a  women or a group of women. We can list the following differences between fertility and fecundity:

Difference between fertility and fecundity

Fertility

• It is the observed capacity to produce children
• It is modifiable. People can increase or decrease their fertility as per their needs and desires.
• It refers to the actual reproductive performance of an individual or a group.
• It is quantitative and expressed with numbers.
• Fertility is affected by fecundity .
• It starts from the sexual relations and conception.
• It is exhibited by females only. 
• Fertility play direct role in population growth.

Fecundity

• It is the biological capacity to produce children.
• It is non-modifiable and directly determined by heredity.
• It refers to potential reproductive performance of an individual or a group.
• It is qualitative and cannot be expressed exactly with numbers.
• Fecundity is not affected by fertility.
• It starts with the menarche and pubescence.
• It is exhibited by males and females both
• Fecundity has indirect role in population growth.

Demographic Measures

Demographic measures are the tools which determine the effect of demographic components and processes in the changes of population characteristics . The change in demographic components and demographic processes ultimately bring changes in population characteristics. Demographic measures are the mathematical calculations methods for the study of demographic situation of a certain place that causes the population changes over the period of time. There are three main demographic measures. These are fertility rates, mortality rates and migration rates. In order to calculate various types of demographic measures, we need the mid-year population. Mid-year population is the average population of a year. There is no constant population throughout a year, but mid-year population represents the average population of the whole year. Mid-year population can be taken in two ways. The first way is an easy one , in which the population on the first day of the seventh month, or on July 1st (kartik 1st for BS year) is taken as the mid-year population. The second method uses the concept of average and is calculated by using the following formula:

Mid-year population (MYP) =Population in the beginning of  the year +Population at the end of the year/2