If the number is greater than 100 there are more

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.
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6. 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 check
was 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 dire
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