84%(151)127 out of 151 people found this document helpful
This preview shows page 519 - 520 out of 658 pages.
If the number is greater than 100, there are more males than females; if it is less than 100, there are more females than males. In the United States, the estimated sex ratio for 2006 was 97.1, which means there were about 97 males per 100 females. Although approximately 124 males are conceived for every 100 females, male fetuses miscarry at a higher rate. From birth to age 14, the sex ratio is 105; in the age 40 – 44 category, however, the ratio shifts to 99.3, and from this point on, women outnumber men. By age 65, the sex ratio is about 84.6—that is, there are 84 men for every 100 women. The ratio of males to females varies among racial and ethnic categories in addition to varying by age. For demographers, sex and age are significant population characteristics; they are key indicators of fertility and mortality rates. The age distribution of a population has a direct bearing on the demand for schooling, health, employment, housing, and pensions. The current distribution of a population can be depicted in a population pyramid—a graphic representation of the distribution of a population by sex and age. Population pyramids are a series of bar graphs divided into five-year age cohorts; the left side of the pyramid shows the number or percentage of males in each age bracket; the right side provides the same information for females. The age/sex distribution in the United States and other high-income nations does not have the appearance of a classic pyramid, but rather is more rectangular or barrel-shaped. By contrast, low-income nations, such as Mexico and Iran, which have high fertility and mortality rates, do fit the classic population pyramid.Pages: 508, 513LO: 16.From a global context, explain the Malthusian perspective on population growth. Answer: English clergyman and economist Thomas Robert Malthus was one of the first scholars to systematically study the effect of population. Displeased with societal changes brought about by the Industrial Revolution in England, he argued that “the power of population is infinitely greater than the power of the earth to produce subsistence (food) for man.” According to Malthus, the population, if left unchecked, would exceed the available food supply. He argued that the population would increase in a geometric (exponential) progression (2, 4, 8, 16,) while the food supply would increase only by an arithmetic progression (1, 2, 3,). In other words, a doubling effect occurs. Thus, population growth inevitably surpasses the food supply; and the lack of food ultimately ends population growth and perhaps eliminates the existing population. However, Malthus suggested that this disaster might be averted by either positive or preventive checks on population. Positive checks are mortality risks such as famine, disease, and war; preventive checks are limited to fertility. For Malthus, the only acceptable preventive checkwas moral restraint; people should practice sexual abstinence before marriage and postpone marriage as long as possible in order to have only a few children. Malthus has had a lasting impact on the field of population studies. Most demographers refer to his dire551