Life Expectancy: The number of years that an average person is expected to live is called life expectancy.
Migration: When people move from one place to another in search of livelihood, it is called migration.
Emigration: When people move outside their country, it is called emigration.
Immigration: When people come from another country, it is called immigration.
The population of the USA and Australia has increased because of immigration. On the other hand, the population of Sudan has decreased because of emigration. People from less developed countries usually migrate to the developed countries in search of better employment opportunities.
In case of internal migration, people from rural areas usually migrate to urban areas. Internal migration does not change the size of the population, but changes the composition of population in a particular area.
Some countries are showing high population growth, e.g. Kenya. Some countries, on the other hand, are showing de-growth in population, e.g. UK and many European countries.
The population composition of a country tells about age profile, sex, literacy level, health condition, occupation and income level. Thus, the structure of the population is called population composition.
Population Pyramid: A population pyramid is a graphical representation of population composition. In a population pyramid, the total population is divided into various age groups, e.g. 5 to 9 years, 10 to 14 years, etc. For each age group, the percentage of the total population is subdivided into males and females.
The relative number of children (below 15 years) and that of the elderly (above 65 years) shows the relative number of dependents in the population. The relative number of people in the working age (between 15 and 65 years) shows the relative number of productive people.
The population pyramid of Kenya is very wide at the bottom and very narrow at the top. This means that while the birth rate is very high, so is the death rate. A larger proportion of people below 15 years of age show that the relative number of dependents is very high in Kenya.
The population pyramid of India shows a wider base but the middle portion of the pyramid is in healthy shape. The top is narrow. This shows that there is sizeable proportion of people in economically productive age group. This is a good sign for the economy of India as the number of dependents is not too much.
The population pyramid of Japan shows a wider middle and narrower base and top. This indicates towards a low birth rate and death rate. The relative size of dependent population is less compared to the relative size of population in the economically productive age group. While this is ideal for the present, it does not hold good omen for the future. In future, there would be more elderly and less people in the working age group.
NOTE: These images of poulation pyramid have been taken from NCERT Textbook of Geography Class 8
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