populations, especially as these are influenced by trends in population dynamics.
Two measures of the spatial character of population are fundamental to the work
of population geographers.Population densityindicates the number of people in
a given unit of a standard area. In much of the world population the unit for report-
ing density is a square kilometer, but in the United States and a few other countries
an areal unit of a square mile is usedmore commonly. Maps may be produced
showing population density based on either unit, so one must be certain to use
the same units when comparing maps of population density. However, one of the
shortcomings of examining human population using density is that the figure
reported assumes an equal distribution across the entire area considered. If this is
a large country, it reveals little about the actual spatial arrangement of people
there. For example, the population density reported for the People’s Republic of
China in 2008 was 110 people per square kilometer. But it is far from the case that
every square kilometer of territory in China has 110 people living on it, so the
information is of limited utility.Population distribution, an indication of where
people actually live in aregionor country, usually shown on amap, often provides
a clearer picture of how population and space are related there.
A number of metrics are used when assessing the dynamics of a population. The
Crude Birth Rate (CBR) of a population measures the number of births in a given
year, per one thousand of the existing population. Because this is a rate, it is
reported as a decimal figure. For example, the birth rate in the Philippines in
2010 was estimated to be 26.01, meaning about 26 babies were born for every
one thousand people in the country. The Crude Death Rate (CDR) indicates the
number of deaths in a specified population per one thousand people, and is
reported in the same fashion as the CBR. Considering these two figures together,
one can quickly deduce the basic parameters of growth in a population for a given
year. If the CBR exceeds the CDR, then the population is increasing; if the CDR
exceeds the CBR then the population is shrinking, unless this is offset by additions
to the population throughmigration. But these measures provide information only
for the immediate year, and cannot offer much information regarding the long-
term (meaning in most cases perhaps 20–25 years) trends. However, the Total Fer-
tility Rate (TFR) can serve as a reasonable predictor of longer term trends in pop-
ulations. The TFR calculates the number of children a fertile woman would have
over the course of her reproduction years, based on the current year’s average. A
“fertile woman” is generally considered to be between the ages of 15 and 49,
and all women in a population are assumed to be fertile. By examining the trends
in the TFR for any population over time, conclusions may be drawn concerning
population growth. The TFR for the entire world in 1950 was almost 5; by 2010
it had dropped to around 2.5, indicating that the growth rate for the planet as a
whole is declining. Some demographic models established by the United Nations260 Population