Lecture 4 Flashcards
What is human demography (HD)?
HD studies changes in population size, structure and geographic distribution
(HD) Changes in population size, structure and geographic distribution are the result of?
fertility, mortality, and migration
why should health researchers care about demography and factors that affect population dynamics?
- demography
- economic, social, cultural factors as well as ecological and biological processes
- population health
All affect one another
HD is nourished by many different disciplines that analyse different aspects of the relationships between economic, social, cultural and biological processes that affect population dynamics such as: economic, sociology, history, biology, anthropology, etc.
what does an expanding population pyramid look like?
super wide at the bottom (young years) and gets super thin at the top (older years)
Stationary pyramid
relatively equal medium width throughout all years until late years very thin
- zero growth
constrictive pyramid
thinner at the bottom/younger years, wider in upper middle and relatively equal till latest years
- negative growth
how is population growth measured?
r = birth rate + [net migration] - death rate
net migration = immigration - emigration
crude mortality rates
m = (d/r) 1000
d = number of deaths during a year
r = number of individuals “at risk of dying”
age specific mortality rates
mx = (dx/Nx) 1000
d = number of deaths to individuals in the 4th age category during a year
N = number of individuals in the 4th age category
x = can be infants or other variables
mortality - two important parameters
- life expectancy
- average number of years remaining for an individual (e.g., life expectancy at birth) - age patterns of mortality
- age-specific mortality rates (fraction of cohort alive at the START OF THE INTERVAL)
- age specific mortality curves
what are some variability in mortality
sex differentials: women tend to live longer than males (with som exceptions) in contemporary industrialised populations
- geographic variation within populations
- variation between nations
life expectancy by country
World population as a whole = 73.4 years (76 females/70.8 males)
Longest life expectancy at birth - Hong Kong: total pop: 85.83 years, males:83, females:88.66
Shortest life expectancy at birth - Chad: 53.68 years, males:52.01, females:55.41
Developed countries: mortality started decreasing around 1920
biological regulation of human fertility
- variation in male and female fecundity
variation in female fecundity is critical for HD due to what factors?
- age
- energetics (pregnancy, childbirth, and lactation, require significant energy)
- lactation (Prolonged lactation can lead to longer inter-birth intervals which reduce the overall reproductive rate. Successful lactate can be influenced by health, nutrition, and SES, which affects child survival rates and maternal health)
- disease
- social environment
variation in female fecundity with age explained by changes in:
- ovarian hormone levels
- frequency of ovulation
- size of the follicle before ovulation
- thickness of the uterine lining
- fetal loss
how can these variations of female fecundity affect population growth?
by affecting reproductive rates (either by slowing them down and or speeding them up)
However, faster reproductive rates (shorter IBI) do not always result in population growth as they can be associated with shorter life spans via increased maternal and child morbidity and mortality
biological regulation of human fertility - variation in female fecundity - diseases
disease
- STDs: blockage of the fallopian tubes
- infections during childbirth: damage to the reproductive tract
- malaria: increase rate of embryonic loss
social regulation of human fertility
Regulation of the formation of reproductive unions:
- variability in age at which unions are formed
- percentage of women who never marry
Exposure to intercourse
- who has sex with whom and when
Probability of conception and birth, given intercourse
- pattern of intercourse
- behavioural regulation of probability of conception and live birth
Patterns of intercourse within reproductive unions:
- spousal separations in migrant labor populations
- honeymoon effect: frequency of intercourse is highest early into marriage
- cultural festivities (e.g., August vacation)
- sexual taboos (e.g., postpartum taboo)
Behavioural regulation of probability of conception and live brith:
- contraceptive use (to limit family size, to space births)
- legislation and attitudes towards elective abortion
the epidemiology transition: changes in mortality patterns
Population growth seen as a result of improvements in sanitary conditions, medical innovations and improvements in nutrition and quality of life in general
demographic transition
- transition from high death and birth rates to low death and birth rates
Associated factors:
- energetic resources
- contraceptive methods
Negative social attitudes towards larger families and increased cost per offspring
changes in mortality patterns - traditional view for the demographic transition
Sanitation and medical innovation resulted in a shift from a greater proportion of infectious diseases (measles, tuberculosis) and resource scarcity to a greater proportion of degenerative disease (cancer, CVD) and problems associate with over abundance of resource and sedentarism (obesity, non insulin dependent diabetes)
changes in mortality patterns in West Europe - McKeown’s Study Findings
McKeown’s study of the historical decline in mortality in England and Wales between 1860-1971 examined four potential causes
- host-parasite interactions
- introduction of effective sanitary systems
- development of modern medicine
- improvements in nutrition
Proximate and ultimate causes of the variation in mortality
Introduction of effective sanitary systems
- specific studies suggest that about 20% of the overall decline in mortality is attributable to improvements in sanitation
Modern medicine
- the decline in mortality due to the development of effective treatments (e.g., decline in tuberculous preceded development of streptomycin by at least 100 years)
Changes in mortality patterns - improvement in nutrition - McKeown
- McKeown concluded that if all other factors are eliminated, the one remaining, nutrition, must be corrected
- Little empirical evidence supporting the hypothesis that nutrition alone could explain these transitions
Perhaps the demographic transition can result from multiple factors acting in synergy
what is migration?
a permanent or semi-permanent change in location to a completely new geographical region
crude net migration rate (CNMR)
CNMR = IMR-OMR
IMR = (IM/p)*1000
OMR = OM/p1000
IMR = immigration rate
OMR = emigration rate
IM = migrants who moved into a region during a given year
OM = migrants who moved out of the region during a given year
p = total midyear population
Emigration vs immigration
Emigration is specifically used to indicate people leaving the country in question.
Immigration is specifically used to indicate people arriving at the country being discussed.
Factors leading to migration
Voluntary internal migration
- following industrial development (better jobs and wages)
- from the country side, following urbanisation (better access to jobs, education, healthcare)
- urban-to-urban migration may decline with improved communication (working remotely)
Invasion migration
- uncontested migration: migration into a region previously unoccupied by humans
- contested migration: migration into a region occupied by another population (can lead to conflicts over resources, land, and cultural differences)
Variability in levels of migration - forced migration
- slave trade
- deportation of prisoners (e.g., Australia)
- War refugess
- economic escapees?
what did epistemology abandon and favour more?
epistemology has abandoned inductivism in favour of more hypothetic-deductive approaches
two historical and economic factors that need to be considered when making demographic predictions
- increase in consumption
- inequities in resource distribution and opportunities and power differentials at local and global levels
most demographic transitions have involved a population size increase followed by either a stabilisation process or in some cases population decreases … yet…
Yet, despite technological advances, and wars, pandemics, natural disasters, etc.. the world population continues to grow
what is the only notable world event that interrupted population growth?
the decline of the Roman Empire and the spread of the bubonic plague in Europe are the only notable interruptions in an otherwise accelerating trajectory of population growth
population momentum
- the world population will continue to expand due to momentum from previous generations where growth rates were higher
- China’s one-child policy introduced in 1980s. To enforce it the government created birth permits and in some cases used forced sterilisations and forced abortions
- it did create a below-replacement growth rate but, due to momentum, growth did not stop until 2021
what is one consequence of large population sizes/large consumption?
pollution
- refer to photo
- lowered fertility alone produces no solution to the population-consumption dilemma (Low 2001)
- the total impact a population has on its environment is a combination of fertility rates and levels of consumption
reduced fertility does not mean reduced consumption
developed countries use 15-20 times the resources per child than developing countries
The number of people the world can support, its “carrying capacity” will depend on the fertility-consumption trends of the population
population and consumption regulation NOW
human population cannot continue to grow indefinitely. we either stop population growth ourselves, or nature will do it for us
consumption cannot continue to increase indefinitely. we either moderate consumption per capita or nature will do it for us
