Demography is the study of the size, composition, and distribution of human populations
• A population is all the people living in a specified geographic area.
• During the past fifty years, the world’s population has more than doubled, growing from 2.5 billion in
1950 to over 6 billion today (80 million persons annually). At this rate, the world population will double
again in the next 50 years.
• Even today, more than 1 billion of the world’s people do not have enough food and lack basic health
care. Will the earth’s resources be able to support a larger population?
• Fertility refers to the number of children born to an individual or a population.
• The most basic measure of fertility is the crude birth rate—the number of live births per 1,000 people
in a population in a given year. The crude birth rate is used to gauge fertility because it is based on the
entire population and does not take into account the variables that affect fertility, such as age and
• In 1998, there were 3.9 million live births in the United States, yielding a crude birth rate of 14.4 per
1,000. This rate was down slightly from 16.6 per 1,000 in 1990.
• Despite a worldwide drop in fertility rates, population is increasing, with the world adding 78 million
more people every year—the population of France, Greece, and Sweden combined—or the equivalent
of a city the size of San Francisco every three days! Each day in 2000, there were 359,000 births and