8.1 Human Populations

Crude Birth Rate (CBR)

The number of live births per 1,000 people in a population per year.

Crude Death Rate (CDR)

The number of deaths per 1,000 people in a population per year.

Natural Increase Rate (NIR)

The annual rate of population growth calculated as (CBR - CDR) / 10, expressed as a percentage.

Doubling Time

The number of years required for a population to double in size at its current growth rate, calculated using the Rule of 70 (70 / NIR%).

Total Fertility Rate (TFR)

The average number of children born to a woman during her childbearing years.

Replacement Rate

The TFR required for a population to exactly replace itself from one generation to the next without migration (approximately 2.1).

Life Expectancy

The average number of years a person can be expected to live based on current demographic conditions.

Inflows (Inputs) to Population

Births and immigration into a population stock.

Outflows (Outputs) from Population

Deaths and emigration out of a population stock.

Net Migration Rate

The difference between immigration and emigration per 1,000 people per year (Immigration Rate - Emigration Rate).

Demographic Transition Model (DTM)

A model describing how birth and death rates change over time as a country develops economically through 5 distinct stages.

DTM Stage 1 (High Stationary)

High birth rate and high death rate resulting in a low, stable total population (agrarian societies).

DTM Stage 2 (Early Expanding)

High birth rate and rapidly falling death rate due to improved healthcare/sanitation, causing rapid population growth.

DTM Stage 3 (Late Expanding)

Falling birth rate and low death rate, leading to population growth at a decelerating rate.

DTM Stage 4 (Low Stationary)

Low birth rate and low death rate, resulting in a high, stable or slowly growing total population.

DTM Stage 5 (Declining)

Very low birth rate falling below the death rate, leading to population aging and overall population decline.

Age-Sex Pyramid

A graphical model showing the distribution of various age groups and genders within a specific population.

Population Momentum

Continued population growth even after fertility rates fall below replacement level, caused by a large proportion of the population entering reproductive age.

Dependency Ratio

The ratio of economically dependent individuals (under 15 and over 65) to the working-age population (15–64).

Demographic Dividend

The temporary economic growth potential resulting from a shift in a population's age structure, where the working-age population is larger than the dependent population.

Direct Population Policies

Government actions directly targeting demographic variables, such as family planning laws, child limits, or financial birth incentives.

Indirect Population Policies

Government measures that influence demographic rates indirectly through broader social or economic developments, such as improving female literacy or healthcare access.

Antinatalist Policy

Government policies designed to reduce birth rates and slow down rapid population growth (e.g., China's historical One-Child Policy).

Pronatalist Policy

Government policies designed to increase birth rates and encourage larger families (e.g., subsidized childcare, paid parental leave, cash bonuses).

Environmental Migration

The movement of people forced or choosing to leave their homes due to sudden-onset (floods, wildfires) or slow-onset (sea level rise, desertification) environmental degradation.

Planetary Boundaries Model

A framework identifying nine Earth system boundaries within which humanity can continue to develop and thrive safely.

Degrowth (HL)

An ecological economics approach advocating for a planned reduction of material and energy consumption in high-income nations to restore ecological balance.

Push Factors

Negative factors in a home region that compel people to emigrate (e.g., poverty, war, natural disasters).

Pull Factors

Positive conditions in a destination region that attract immigrants (e.g., job opportunities, political stability, better services).