Chapter 18 Population Changes

Chapter Outline  Demographic Techniques  Preindustrial Population Trends  Malthusian Theory  Modernization and Population  The Demographic Transition  The Second Population Explosion  The Population Explosion Wanes  “Depopulation”

Growth Rate of a Population  The net population gain (or loss) takes three variables into account: –The increase (or decrease) in births. –The increase (or decrease) in deaths. –The increase (or decrease) due to migration.

Rates  Allows comparisons between years in which the total population differed in size.  In 1910, there were 2,777,000 live births in the United States.  In 1996, there were 3,915,000 live births.  In 1910, fertility was higher. There were fewer than half as many people in 1910 as in 1996 to produce those births.

Preindustrial Population Trends  Primitive societies had difficulty maintaining their populations.  Historians believe that in primitive groups about 50% of all children died before the age of five.  10,000 years ago, after at least 3 million years of human reproduction, there were only about 5 million human beings on the earth.

First Great Shift in Human Population  Beginning about 10,000 years ago, population grew due to the development of agriculture.  With a better diet, we became healthier, and reproductive rates began to exceed death rates.  8,000 years later, by A.D. 1, the worldwide human population was about 300 million.

Causes of Periodic Declines in the Population  Famine  Disease  War

Malthusian Theory  Populations will always rise to the level of subsistence.  Malthus identified the limits to growth, famine, disease, and war, as positive checks that kept populations proportionate to the food supply.

Second Great Shift in Human Population: Industrial Revolution  In England, where the Industrial Revolution began, the population was 3 times larger by 1841 than it had been in  In 1650, Europeans made up 18% of the world’s population, in 1920 they made up 35%.  There was a virtual disappearance of nutritional deficiency diseases as causes of death in western Europe.

Third Great Shift in Human Population: Demographic Transition  A change from the pattern of high fertility and high but variable mortality to low mortality and fertility.  Increased food supplies and the conquest of diseases caused mortality to fall.  As mortality continued to decline, fertility also began to decline in the 1860s.  Growth ceased by the 1930s because fertility no longer exceeded mortality.

“Thresholds” That Must Be Crossed To Reduce Fertility  More than half of the labor force is not employed in agriculture.  More than half of the persons age 5 to 19 are enrolled in school.  Average life expectancy reaches 60 years.  Infant mortality falls to 65 deaths per 1,000  80% of females age 15 to 19 are not married.  Per capita GNP reaches $450.  At least 70% of adults can read.

Demographic Transition Thresholds and Fertility in China’s Provinces Threshold Correlation with Fertility rate 1. Percent not employed in agriculture– Percent high school graduates– Life expectancy– Low rate of infant mortalityNot available 5. Low rate of teenage marriageNot available 6. Affluence: GNI per capita–.74 Percent of farms with TVs–.65 Percent of farms with phones– Literacy–.67

Fourth Great Shift in Human Population  Unprecedented population growth in the less developed nations.  Throughout the 1950s and 1960s, the population in less developed nations grew from 2 to 3.5% a year.  In the early 1970s, the world’s population was growing at a rate that would double its size every 37 years.  If that rate were to hold for 200 years, instead of 6 billion people on earth, there would be 157 billion!

Reasons for the Population Explosion  Pesticides  Better agricultural methods  Vaccinations against disease  Better nutrition  Cleaner water

Fifth Great Shift in Human Population  Fertility began to decline in most of the less developed nations.  In Latin America, back in 1965 the average woman in Brazil bore 5.7 children.  Today, she has 2.1 children, below replacement level, given Brazil’s rate of infant mortality.

Sixth Great Shift in Human Population  Beginning in the 1960s, fertility rates in industrialized nations were below replacement levels.  In Thailand in 1965, the average woman gave birth to 6.3 children; in 2001, to only 1.9 children.

Effects of Fertility Rate Continuing to Fall  Populations of European nations will shrink, unless offset by immigration.  The “native” populations will become very elderly.

6 Major Shifts in Human Population Patterns 1. The invention of agriculture permitted the population to begin to grow rapidly. 2. Industrialization stimulated a long period of uninterrupted growth, sometimes referred to as the first population explosion. 3. Population growth was halted by a decline in fertility, called “the demographic transition”.

6 Major Shifts in Human Population Patterns 4. After World War II, a population explosion in the less developed nations was caused by decreased mortality and increased food supplies. 5. Sharply falling fertility in most of the less developed nations as they underwent the demographic transition. 6. Fertility rates have continued to fall and now are well below the level needed for replacement.