AP Human Geography
Chapter 2 Key Issue 2 – Where Has the World’s Population Increased?
Study Guide Notes
Population increases rapidly in places where many more people are born than die, increases slowly in
places where the number of births exceeds the number of deaths by only a small margin, and declines in
places where deaths outnumber births.
The population of a place also increases when people move in and decreases when people move out.
This element of population change – migration – is discussed in Chapter 3. Geographers…measure
population change…through three measures:
1) Crude Birth Rate (CBR) – the total number of live births in a year for every 1,000 people
2) Crude Death Rate (CDR) – the total number of deaths in a year for every 1,000 people
3) Natural Increase Rate (NIR) the percentage by which a population grows in a year
The term natural means that a country’s growth rate excludes migration. The term crude means that we
are concerned with society as a whole rather than a refined look at particular individuals or groups.
Natural Increase
The world natural increase rate during the first decade of the 21st century is 1.3%. The world NIR is lower
today than its all-time peak of 2.2% in 1963. However, the NIR during the second half of the 20th century
was high by historical standards. The number of people added each year has dropped much more slowly
than the NIR, because the population base is much higher now than in the past. The rate of natural
increase affects the doubling time, which is the number of years needed to double a population. When
the NIR was 2.2% back in 1963, the doubling time was 35 years.
Virtually 100% of the natural increase is clustered in less developed countries. To explain these
differences in growth rates, geographers point to the regional differences in fertility and mortality rates.
Fertility
The highest crude birth rates are in sub-Saharan Africa, and the lowest are in Europe. Geographers also
use the total fertility rate (TFR) to measure the number of births in a society. The TFR is the average
number of children a women will have throughout her childbearing years. The TFR for the world as a
whole is approximately 3. The TFR exceeds six in many countries of sub-Saharan Africa, compared to less
than 2 in nearly every European country.
Mortality
2 useful measures of mortality in addition to CDR…are the infant mortality rate and life expectancy. The
infant mortality rate (IMR) is the annual number of deaths of infants under 1 year of age, compared with
total live births…usually expressed as the number of deaths…per 1,000 births rather than as a
percentage. IMR exceeds 100 in some LDCs. In general, the IMR reflects a country’s health-care system
Minorities in the USA have IMR that are twice as high as the national average, comparable to levels in
Latin America and Asia
AP Human Geography
Chapter 2 Key Issue 2 – Where Has the World’s Population Increased?
Study Guide Notes
Life expectancy at birth measures the average number of years a newborn infant can expect to live at
current mortality levels. Babies born today can expect to live into their late 70s in Western Europe, but
only into the late 40s in many sub-Saharan African countries.
Higher rates of natural increase, crude birth, total fertility, and infant mortality, and lower life
expectancy are in LDCs. The final world map of demographic variables – crude death rate – does not
follow the familiar pattern. The combined crude death rate for all LDCs is actually lower than the
combined one for MDCs. The populations of different countries are at various stages in an important
process known as the demographic transition.