Population Growth Lecture PDF

POPULATION GROWTH  WORLD POPULATION GROWTH Human being in the last 250 years has begun to accelerate , around the time of agrarian revolution; The world population was estimated at about 4million people. Until then, human beings were primarily hunters and gathered and so they used res...

POPULATION GROWTH  WORLD POPULATION GROWTH Human being in the last 250 years has begun to accelerate , around the time of agrarian revolution; The world population was estimated at about 4million people. Until then, human beings were primarily hunters and gathered and so they used resources extensively, between 8000BC and 5000 BC, With an average of 372 people , added to the world population yearly. By the time of Christ, the population growth rate had increased to 300,000 people per year The total population was estimated at 200 million people The top5 countries by population today are: China, India,  World Population Growth Through History Human population has grown very slowly for most of its existence on earth Scientists currently estimate that modern human beings (Homo sapiens) evolved roughly 130,000 to 160,000 years ago. Many threats, from diseases to climate fluctuations, kept life expectancy short and death rates high in pre-industrial society, it took until 1804 for the human population to reach one billion From that point forward, however, population growth accelerated very quickly. Thousands of people died from infectious diseases such as typhoid and cholera, which spread rapidly in the crowded, filthy conditions that were common in early factory towns and major cities, or were weakened by poor nutrition.  WORLD POPULATION MILESTONE World Population Year Time to add 1 reaches billion 1billion 1804 2 billion 123 years 1927 3 billion 33 Years 1960 4 billion 14 years 1974 5 billion 1987 13 years 6 billion 1999 12 years Major Milestones But from about 1850 through 1950, a cascade of health and safety advances radically improved living conditions in industrialized nations. Major milestones include: improving urban sanitation and waste removal; improving the quality of the water supply and expanding access to it; forming public health boards to detect illnesses and quarantine the sick; researching causes and means of transmission of infectious diseases; developing vaccines and antibiotics; adopting workplace safety laws and limits on child labor; and promoting nutrition through steps such as fortifying milk, breads, and cereals with vitamins. Population growth in the 20th century By the mid-20th century, most industrialized nations had passed through the demographic transition. As health technologies were transferred to developing nations, many of these countries entered the mortality transition and their population swelled. The world's population growth rate peaked in the late 1960s at just over 2 percent per year (2.5 percent in developing countries). Demographers currently project that Earth's population will reach just over nine billion by 2050, with virtually all growth occurring in developing countries  Fertility Trend Future fertility trends will strongly affect the course of population growth. This estimate assumes that fertility will decline from 2.6 children per woman in 2005 to slightly over 2 children per woman in 2050. If the rate falls more sharply, to 1.5 children per woman, world population would be 7.7 billion in 2050, whereas a slower decline to 2.5 children per woman would increase world population to 10.6 billion by 2050.  Population growth in the 21st century World population growth in the 21st century will be different from previous decades in several important ways. First, humans are living longer and having fewer children, so there will be more older people (age 60 and above) than very young people (age zero to four). Second, nearly all population growth will take place in urban areas. Third, fertility rates will continue to decline. All of these trends will affect nations' economic development. Senior citizens can be active and productive members of society, But they have many unique needs in areas ranging from medical care to housing and transportation. Growing elderly populations will strain social services, especially in countries that do not have well developed social safety nets to guarantee adequate incomes for older citizens. In countries that have "Pay As You Go" social security programs, increasing ratios of older to younger people may create budget imbalances because fewer workers are paying funds into the system to support growing numbers of retirees.  As societies age, demand for younger workers will increase, drawing more people into the labor force and attracting immigrants in search of work. Declining fertility rates allow more women to work outside of the home, which increases the labor supply and may further accelerate the demographic transition As fertility rates fall, some countries have already dropped below replacement level—the number of children per woman that keeps population levels constant when births and deaths are considered together over time (assuming no net migration).  DEMOGRAPHIC CHANGES Changes in the population occur as a result of the combination of mortality, fertility and migration The interaction of these demographic variables can be presented in the form of an equation as shown below: (pt+n)=PT+B+D+M (pt+n) means population today PT means population at a present pt in time B means birth D means death M means migration Population change = Natural increase (birth and death) + migration  AGE/SEX STRUCTURE To observe changes in the population, we need to look at the age and sex structure of the population For example, changes in fertility will affect the number of children born. Please Note: A Population is considered old if more than 10% of its people are older than 65 years. And young if more than 35%of its population is under 15 years of age The age structure can be showing statistically or represented graphically in three ways: By constructing a population pyramid; By calculation the average age of the population and By calculating dependency ratio  POPULATION PYRAMID Population pyramid is a graphical representation of the distribution of population by age and sex. In developing countries, there is much birth and where numbers of elders are relatively few. In developed countries where birth are relatively low, the average age of population is usually calculated using the median. The dependent population is defined as those under 14 years and 65 years.  THEORY OF DEMOGRAPHIC CHANGE Theory of demographic change is demographic transition theory Originally it was not a theory but description by Warren Thompson concern for demographic changes that take place in certain countries. In 1929, he published data which showed that countries could be grouped in three main categories depending on the patterns of population growth. Group A (Stage 1 or Highest stationary) North Europe and United States had moved from highest death rate and highest birth rate which canceled each other Group B- (Stage 2 or early expanding) The death rate begins to decline while the birth rate remains unchanged. Group C-(Stage 3 or late expanding) The death rate decline still further, and birth rate tends to fall, the population continue to grow , because births exceed deaths. Group D- (Stage 4 or Low stationary) This is characterized by a low birth and low death rate with the result that the population becomes stationary Group E-(Stage 5 or Declining) The population begins to decline because birth rate is reduced also the death rates