(e.g. in response to below replacement fertility)
may promote new modes ofbelongingand
family strategies, and create the conditions
for another distinctive transition. ajb
Suggested reading
Kirk (1996); Van de Kaa (1987).
demography The science of human popu-
lations. For much of the preceding 400 years,
the field has concerned itself with the size,
distribution and composition of populations,
and how changes in these are connected with
the three population processes ofmortality,
fertilityandmigration(Greenhalgh, 1996).
Whileformal demographyhas developed math-
ematical and actuarial techniques to model
and project changes in population (seelife
table;population projection), the interdis-
ciplinary field ofpopulation studiesexamines
demographic change within its broader soci-
etal setting and makes use of a wide range of
approaches (see, e.g., historical demog-
raphy;life course). Despite its keen interest
in population distribution, its interdisciplinary
niche and its strong connections with soci-
ology and economics,demographyhas had
a relatively limited engagement withgeog-
raphy. Although the development ofpopula-
tion geographybetween the 1960s and the
1980s and the growth ofspatial demography
drew attention to the study of mortality, fertil-
ity and particularly migration, many geograph-
ical analyses of issues including poverty,
gender roles, social exclusion,urbanization
and environmental degradation underplay
population factors (but for a recent exception,
see Gould, 2005).
Descriptions of changes in population size
and distribution make use of empirical data on
deaths, births, moves and the ages at which
these events occur, mostly obtained from
populationcensuses, social surveys or regis-
ters of population. Population growth within
an area is most simply expressed through the
balancing equation as follows:
Pt 2 ¼Pt 1 þ(Bt 1 t 2 Dt 1 t 2 )
þ(It 1 t 2 Et 1 t 2 ),wherePis the population size,Bis births,Dis
deaths,Iis in-migrants to an area,Eis out-
migrants from an area,t2 is time 2,t1 is time
1 in the past, andt1–t2 is the time interval
between time 1 and time 2. Knowledge of the
ages at which vital events occur allows age-
specific rates to be used to createsyntheticor
modelpopulations that approximate actualage
compositions of populations, and may be
used to project future population scenarios
(see population projection). Such stable
population theoryis at the basis oflife tables
that are used to calculatelife expectancyby
age, the number of survivors byage, and thus
the impact of the three population processes
upon the age structure, and vice versa. Armed
with such data, research on changes in popu-
lation growth and distribution has centred
on efforts to build, critique and extend the
demographic transitionmodel; for example,
through work on differentials inmortality,
the onset of fertility decline and, more
recently, its recovery (Bongaarts, 2002; Case
and Paxson, 2005).
The field has long enjoyed an extremely
close–somehaveargued,tooclose–relationship
with social policy, whether at the international
scale such as the League of Nations’ commis-
sioning of the Office of Population Research’s
work on transition theory in the 1940s, or in
informing the US administration’s laissez-faire
position on family planning at the 1984
International Conference on Population and
Development, or more recently in assessing
the impact of immigration policy or welfare
reform measures upon the life chances of
low-income family members (Bu ̈che and
Frick, 2005). A good deal of research effort
continues to debate new dimensions of the
population–resource–well-being nexus in
light of the likely globaldiffusionof low fer-
tility andageing, and the short-termism of
replacement migration policies (Meyerson,
2001). Connected to this, studies in family
demography describe factors behind changes
in the timing and nature of decisions about
marriage and partnering, divorce and house-
hold dissolution, leaving and rejoining the par-
ental home, cohabitation, and transitioning
from full-time to part-time and unpaid work
(Holdsworth and Elliot, 2001). The diversifi-
cation and plurality ofhouseholdsis a theme
in work on, for example, mixed marriages,
and variations in intergenerational relations
and resource flows byclass, gender, race
andethnicity(Gershuny, 2000). Many ana-
lyses link family demography to well-being,
with an increasing emphasis upon children
(Eloundou-Enyegue, 2004). Applied research
includes the development of geographical
informational systems and geodemo-
graphictechniques; both are used by market-
ingfirmstotarget launch new products and
design sales areas, and by local authorities to
deliver services more efficiently. ajbGregory / The Dictionary of Human Geography 9781405132879_4_D Final Proof page 153 1.4.2009 3:15pmDEMOGRAPHY