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ENVIRONMENTAL SCIENCE

ENVIRONMENTAL SCIENCE. The Human Population: Demographics Part IV Dynamics of Population Growth. Part 4 Dynamics of Population Growth Objectives. Read and interpret population profiles. Discuss the need for population projections. List the phases and describe demographic transition.

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ENVIRONMENTAL SCIENCE

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  1. ENVIRONMENTAL SCIENCE The Human Population: Demographics Part IV Dynamics of Population Growth

  2. Part 4 Dynamics of Population Growth Objectives • Read and interpret population profiles. • Discuss the need for population projections. • List the phases and describe demographic transition.

  3. Population Profiles • A population profile is a bar graph showing the number or proportion of people (male and female separately) at each age for a given population. • A detailed census is taken every ten years in most countries. • Demography is the science of collecting, compiling, and presenting information about populations. • The proportion of people in each age group at a given date provides a snapshot of a population that shows the age structure of the population.

  4. Population Profiles • The proportion of people who die before age 60 in developed countries is small, so the population profile below age 60 is an echo of past events as reflected by birth rates. • Population profiles provide governments and businesses with a way of realistically planning for the future demands of a society for various goods and services. • With the increase in the number of retirees over the next few decades, the Social Security System will be unable to pay 100% of promised benefits unless changes are made – if no changes are made, it may be only able to pay up to 73% of the promised benefits.

  5. Population Projections • Simple subtraction of deaths from births gives the absolute change in the size of the population. • One can estimate the birth rates by noting the number of young women moving into reproductive ages and factoring in the percentage of women at each age having offspring. • Actuarial tables are used by insurance companies to determine life insurance rates based on statistics regarding deaths in various age groups.

  6. Population Projections • Changes in fertility rates and longevity make predictions about populations difficult. • Graying is the term used to indicate that the proportion of elderly people is increasing. • Low fertility rates and prospective declining population typify highly developed nations, except for the U.S. • Even though fertility rates in some developing countries are declining, they are still well above replacement levels.

  7. Population Projections • Population profiles for developing countries tend to have a pyramid shape. • Population momentum is observed when countries have a pyramid shaped population profile, if their total fertility rate drops to replacement level, they still experience growth for another 50-60 years. • Population momentum occurs because of the disproportionate percentage of the population entering their reproductive years.

  8. The Demographic Transition • As economic development occurs, human societies tend to move away from a primitive stability (high birth rates offset by high infant and childhood mortality) and toward a modern population stability (low infant and childhood mortality balanced by low birthrates). • The basic premise of the demographic transition is that there is a causal link between modernization and a decline in the birth and death rates.

  9. The Demographic Transition • Crude Birth Rate (CBR) and Crude Death Rate (CDR) is the number of births and deaths per 1,000 of the population in a year. • CBR – CDR = Natural increase or decrease in population per 1,000 per year/10 = %. • The doubling time of a population is the number of years it will take a population growing at a constant percent per year to double.

  10. The Demographic Transition • CDR used to be about 40 per 1,000, but has dropped to an average of about 11 per 1,000 and is referred to as epidemiologic transition. • Fertility transition is the observed shift from now-developed countries having a CBR of 40 or 50 per 1,000 down to 8 to 12 per 1,000.

  11. The Demographic Transition • There are four phases of demographic transition. • Phase I is primitive stability with a high CBR and a high CDR offsetting one another • Phase II is marked by a declining CDR (epidemiologic transition) and a high CBR resulting in accelerated population growth • Phase III is marked by a declining CBR, but is still experiencing significant population growth • Phase IV is marked by a balance between a low CBR and a low CDR

  12. The Demographic Transition • Developed countries tend to fall into Phase IV of demographic transition while developing countries fall into Phase II or Phase III. • Modernization and demographic transition take many years to develop. • Modernization before population growth is curbed may undercut the economic success of a nation.

  13. The Demographic Transition • The consumption oriented life-style of those in countries that have completed demographic transition place the greatest stress on our world. • There is only a correlation between development and demographic transition.

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