POPULATION GROWTH AND DECLINE OVER TIME AND SPACE
Historic trends and projections for the future
For much of human history, Earthís population was relatively small
? estimated at about10 million people. It was also relatively stable,
fluctuating between periods of growth and decline, but never experiencing
dramatic change until about 8000 BC when the First Agricultural Revolution
resulted in a more reliable food supply, which in turn led to gradually
declining death rates and rising rates of natural increase. At the
onset of the Christian era, the worldís population is estimated to have
been about 300 million people. By 1500 it had increased to about 500 million
in spite of wars, famines, and plagues, and by 1800, to one billion.
Then, as today, Asia dominated, with about 64% of the total population,
followed by Europe with 21% and Africa with 13%.
The mid-18th century saw the beginnings of change with the arrival of the Second Agricultural Revolution that was spawned by the Industrial Revolution. New crop rotation and fertilization practices were developed, more efficient farm tools increased productivity, better transportation systems improved distribution and availability of food, and scientific developments in medicine and sanitation resulted in better health. All of these innovations combined to send death rates spiraling downward, prompting theories of doom, such as Thomas Malthusís prophesy that famine would be the inevitable outcome of the populationís growth exceeding increases in food production.
By 1930, the worldís population had reached the second billion, with most of the growth occurring in the more developed countries of Western Europe and North America. For example, between 1800 and 1900, Europeís population doubled, and that of the United States and Canada, fueled by the combination of natural increase and migration, increased from only 7 million to over 80 million. But the most rapid period of population growth was still to come.
In the post-World War II environment of crumbling colonial empires, the Medical Revolution triggered population growth unlike that previously experienced. The medical knowledge and technology developed over the previous two hundred years in the industrializing countries of Western Europe and North America spread quickly to the newly independent countries of Asia, Africa, and Latin America. The result was a population explosion of dramatic proportions. In 1950, the worldís population was about 2.5 billion. The year 1975 saw 4 billion people, and 1987 saw 5 billion. Although the rate of natural increase leveled off at a little over 2% in the period 1965-1970 due to declining fertility rates and has fallen to the current rate of 1.4%, the total number of people added to Earthís population each year ? almost 80 million annually - remains high because of the very large base population in the less developed regions of Asia, Africa, and Latin America where most growth is now occurring. Declining fertility rates in all regions of the world combined with the deadly impact of HIV/AIDS have slowed population increase. Nevertheless, medium-variant projections by the United Nations indicate a population of 8.9 billion people by the year 2050. Asia is expected to continue to dominate with 59% of the worldís population, and despite the epidemic proportions of AIDS, Africa is projected to have almost 20% of the worldís population, while Europe will have dropped to only 7% .
A shift from high fertility and mortality to low fertility and mortality characterized the 19th century demographic history of most industrialized countries. This pattern led to the formulation of the demographic transition model. The assumption of this model is that all countries will, over time, share a common demographic experience, leading to a low-growth equilibrium. Most interpretations of the model include four stages: high fertility-high mortality/low growth; high fertility-declining mortality/high growth; declining fertility-low mortality/ high, but declining growth; and low fertility-low mortality/low growth. The rate of growth is a function of the gap between fertility and mortality in stages 2 and 3. For most industrial countries, presently in late stage 3 or stage 4, the absolute increase in population has been moderate. However, in most less developed countries, which have begun the transition at a later date, the population increase has been dramatic, if not overwhelming. First of all, in many instances less developed countries began the transition with a much larger population base. Further, the decline in mortality has often been precipitous due to medical assistance and knowledge and technology transfer from industrial countries. In contrast, changes in fertility are closely linked to socio-cultural standards that may or may not respond to demographic change in the same manner as European countries. Consequently, the experience of contemporary less developed countries may be different from that of countries that made this transition in the 19th century. This notwithstanding, the demographic transition model remains a useful tool for evaluating a countryís demographic development if students keep in mind that a model is only a generalization intended to facilitate analysis; it is not meant to be a literal depiction of reality.
Patterns of Fertility, Mortality, and Health
Fertility and mortality, which are central elements of the demographic
transition, exhibit a varied spatial pattern. Total fertility rate refers
to the total number of children a woman can be expected to have during
her childbearing years at current birth rates. In 1950 the average total
fertility rate in the more developed countries was 2.8, while the average
in less developed countries was 6.2, ranging from 6.6 in Africa to 5.9
in Latin America. By 1998 fertility rates had fallen dramatically in most
regions, to a low of 1.4 in Europe and 2.0 in North America ? both below
replacement fertility of 2.1 ? and 2.8 in Asia and 3.0 in Latin America.
Only Africa lags behind in the trend toward lower fertility, where the
average rate remains at 5.6, and in Sub-Saharan Africa, at 6.0. Once again,
however, scale is an issue. Regional averages disguise tremendous variation
among individual countries. For example in Asia, some countries, including
China, South Korea, and Thailand, are at below replacement fertility while
other countries such as Pakistan, Cambodia, and Laos remain at fertility
levels above 5.0. Likewise in Sub-Saharan Africa, the average fertility
of 6.0 includes a range that extends from a low in South Africa of 3.3
to a high in Niger of 7.5 .
Country-level fertility rates, like regional rates, mask significant variations. For example, in the United States, minorities account for 40% of all births, despite the fact that they make up only 28% of the total population . Certain racial and ethnic minorities have higher fertility rates than the majority white population. The national average fertility is 2.0, but the total fertility rate among Hispanics is about 3.0, and among African Americans, about 2.2. Among Asians and Pacific Islanders, however, the total fertility rate falls slightly below the national average, at 1.9. The generally younger age profile of minorities and their higher fertility rates will result in minoritiesí accounting for an increasing proportion of the total population in the future, projected at 39% by 2050. In addition to variations according to race and ethnicity, fertility rates also vary inversely with income and womenís level of education. For example, the fertility rate among women with more than four years of college averages 1.4; among women with a high school education, 2.0; and among women who did not complete high school, 2.7. Further, fertility rates tend to be higher among rural populations than among urban dwellers where couples and single women tend to delay fertility decisions .
The counter-balance to fertility in the demographic equation is mortality. Like fertility, mortality varies widely. Improving health conditions have brought death rates down, first in Europe and North America, and more recently in virtually every country worldwide. Analysis of patterns in death rates is a complex process and must be linked to such concepts as age structure and life expectancy. For example, Libya, a country with a young median age, has a death rate of only 3/000, compared to Sweden, which has an older median age and a death rate of 11/000. Should one infer then, that quality of life in Libya is better than that in Sweden? To the contrary, examination of other indicators of quality of life confirms that conditions in Sweden are better than those in Libya. In other words, death rate is not necessarily a reliable indicator of quality of life because it is especially sensitive to related factors, particularly age structure.
One alternative indicator of quality of life is infant mortality. Children under the age of one year are particularly vulnerable to poor living conditions, inadequate food supply, and lack of sanitation and clean water. Although conditions have improved in recent years, in many less developed countries more than one child in every ten dies before reaching its first birthday. As with crude death rates, infant mortality is highest in Sub-Saharan Africa, where it reaches 170/000 in Sierra Leone. In the United States, infant mortality is 7/000, half what it was only twenty years ago, but still higher than in many European countries, including Germany and Iceland where rates are only 5/000 .
Life expectancy ranges from a low of 36 years in Malawi to a high of 79 years in such countries as Canada, Iceland, Sweden, and Switzerland. Life expectancy in the United States is 77 years, a dramatic improvement over 47 years in 1900, and clear evidence that our population is aging. In fact, the fastest growing cohort in the United States is the group age 85 years and up, termed "oldest old" by the U.S. Census Bureau. Similar improvements have occurred in other countries, including India, Japan, and Russia. Rising life expectancies have been made possible by advances in medical care and disease control. This change in the patterns of mortality, referred to as the Epidemiological Transition, results in major changes in the age structure of the population as the concentration of deaths shifts from younger to older cohorts. For example, in England and Wales in 1891, one-third of all deaths occurred in the youngest cohort (ages 0 to 4 years) and the median age at death fell in the 30-34 year cohort. By 1966, this pattern had shifted dramatically, with less than 5% of deaths occurring before the age of 5 years and more than 40% occurring after the age of 75 years. Median age at death was in the 70-74 year cohort. As with the Demographic Transition, the Epidemiological Transition has been slow to reach the less developed regions. As recently as 1955, almost 50% of deaths in Latin America and the Caribbean occurred in the youngest cohort and median age at death fell in the 5-9 year cohort. The region is projected to make the transition to mortality patterns similar to those of England and Wales by 2030.
Regional Variations of Demographic Transitions
While communicable diseases and preventable health conditions have
been held at bay, non-communicable diseases and degenerative conditions
associated with aging have gained a foothold. For example, in more developed
countries, the leading causes of death are cancer and heart disease, accounting
for almost 60% of deaths in the United States. By contrast, in less
developed countries, the main causes of mortality are HIV/AIDS, tuberculosis,
and pregnancy-related conditions. In Africa especially, the spread of HIV/AIDS
has had a devastating impact on those countries most affected. In Botswana,
for example, it is believed that one person in every four is infected with
this deadly disease, and life expectancy is projected to fall to only 41
years by 2005, twenty-nine years lower than projected without the incidence
of HIV/AIDS .
As with other demographic measures, mortality and life expectancy also vary according to socioeconomic status, race, and ethnicity. For example, death rates are higher among those with lower incomes and among those with lower levels of educational attainment. In the United States, life expectancies of African Americans and Native Americans fall several years below that of the general population. However, life expectancies of Hispanics and Asian Americans are the same and higher, respectively, as the general population .
Effects of Pro and Anti-natalist Policies
At the International Conference on Population and Development in Cairo,
Egypt in 1994, 180 countries endorsed an action plan that calls for improvement
in the status of women, alleviation of poverty, provision of better health
care, including family planning, and protection of the environment . Each
country will draft its own national action plan to achieve these goals,
consistent with it culture and value system. The extent to which individual
countries respond to the Cairo mandate will affect the global population
profile and the spatial dimensions of various demographic characteristics.
Understanding the dynamics of population change at multiple scales is a
central theme of the population unit in the advanced placement human geography
course.
