Population Growth and the Demographic Transition Learning Objectives To view population growth from a .1. Malthusian perspective To calculate crude death rates, birth .2. rates, rates of natural increase, and population doubling times To comprehend the concept of the .3. Demographic Transition
society community Demography a kindred population science the with epidemiology, it shares and theGreek root demos (people)
centurysame founder, 1.7th GrauntEnglishman, John Demography is the scientific study of the determinants and consequences of human population trends Demography is the study of population, including the impact of birth, death, fertility, marriage, migration and other
social factors on population .structure and trends :
T.R. Malthus, 1.766-1.83.4 English clergyman, Thomas Robert Malthus, was the first person to draw widespread attention to the two components of natural increase, births and deaths .(fertility and mortality)
In his Essay on the Principle of Populatio n , initially published in 1.798, Malthus postulated that population tended to grow geometrically (exponentially) while the means of subsistence (food) .grew only arithmetically The Malthusian Trap
arithmetic growth (food): 1., 2., 3., 4, 5, 6, 7, 8, 9, 1.0 geometric growth (population): 1., 2., 4, 8, 1.6, 3.2., 64, 1.2.8, 2.56, 51.2. Malthus argued that the difference between geometric and arithmetic growth caused a tension between the growth of population and that of the means of subsistence. -- this gap could not persist . indefinitely
Owing to war, disease, hunger, and vice, mortality would serve as a positive check on .population growth Solution to the Malthusian Trap Preventive checks: birth control through (2.) (1.) later age at marriage. abstinence from sex . outside marriage
Malthus opposed artificial methods of) birth control on moral grounds. Viewed (contraception as a vice Population Explosion Contrary to Malthuss prediction, mortality has not yet risen to curb .world population growth billion people in 1.800 1 billion by the end of the 6 th 2.0 century
< Population Explosion Why was Malthus unable to foresee the population explosion (also known as ?the population bomb) He did not recognize the force of the Industrial Revolution, which produced exponential growth in the means of .subsistence
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By the beginning of the 2.1. century, world population reached 6 billion. Most of the growth has occurred in the past .2.00 years st
8/5 = 2025 Figure 1. World Population Growth Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Third edition. Population Reference Bureau 53(3); 1998: 38 The unprecedented population growth of modern times heightens interest in the notion of doubling time. Calculation of population doubling time is
.facilitated by the Law of 70 Law of 70 If a population is growing at a constant rate of 1.% per year, it can be expected to double approximately every 70 years if the rate of growth is 2.%,-then the expected doubling time .is 70/2. or 3.5 years
Pt = P0 ( 1+ r )t = Pt t = P0 =
r = t ) Pt + 1 = Pt + ( B D ) + ( I E The Demographic Transition During the first half of the
2.0th century, demographers conceived the notion of the .demographic transition The Demographic Transition The demographic transition framework illustrates population growth in terms of discrepancies and changes in two crude vital rates mortality and fertility (ignores migration)
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5 . -1 . ) 35-45 ( (
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. 1980 CRUDE VITAL RATES = Crude Death Rate (CDR) deaths in calendar year * k#
midyear population CRUDE VITAL RATES = Crude Birth Rate (CBR) deaths in calendar year * k# midyear population CBR - CDR Rate of Natural Increase = Figure 2. The Demographic Transition
Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Third edition. Population Reference Bureau 53(3); 1998: 39 Figure 3. Demographic/ Epidemiologic Transition Framework Source: Ian R.H. Rockett. Population and Health: An Introduction to Epidemiology. Second edition. Population Reference Bureau 54(4); 1999: 9
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