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AP Human Geography (APHG) Demographic Calculator

Calculate Vital Rates, Population Densities, and Dependency Ratios

Vital Statistics

Total Population

Annual Births

Annual Deaths

Land & Density Data

Total Land Area (sq km)

Arable Land Area (sq km)

Number of Farmers

Age Structure (Dependency Ratio)

Pop Under 15

Pop 15 – 64

Pop 65+

Calculation Results

Crude Birth Rate (CBR): –

Crude Death Rate (CDR): –

Rate of Natural Increase (RNI): –

Doubling Time (Rule of 70): –

Arithmetic Density: –

Physiological Density: –

Agricultural Density: –

Dependency Ratio: –

Understanding AP Human Geography Formulas

In Unit 2: Population and Migration patterns, human geographers use specific mathematical formulas to analyze the demographic health and spatial distribution of a country. This tool automates the core calculations required for the AP Human Geography exam.

1. Vital Rates & Growth

Crude Birth Rate (CBR): The total number of live births in a year for every 1,000 people alive in the society.

Crude Death Rate (CDR): The total number of deaths in a year for every 1,000 people alive in the society.

Rate of Natural Increase (RNI): The percentage growth of a population in a year, computed as (CBR – CDR) divided by 10. Note that RNI does not include migration.

Rule of 70 (Doubling Time): To find the number of years it takes for a population to double, divide 70 by the RNI percentage. For example, an RNI of 2.0% results in a doubling time of 35 years.

2. Population Density Measures

Density is not just about how many people live in an area, but how they relate to resources:

Arithmetic Density: Total objects (people) in an area. Formula: Total Pop / Total Land Area.
Physiological Density: The number of people supported by a unit area of arable land. High physiological density suggests high pressure on food production. Formula: Total Pop / Arable Land.
Agricultural Density: The ratio of the number of farmers to the amount of arable land. Developed countries typically have lower agricultural densities due to mechanization. Formula: Total Farmers / Arable Land.

3. Age Structure & Dependency

The Dependency Ratio compares the number of people who are too young or too old to work (under 15 and over 64) to the number of people in their productive years. A high ratio indicates a greater financial burden on those who are working to support the dependents.

Example Calculation:
If a country has 20,000 births, 10,000 deaths, and a population of 1,000,000:
– CBR: (20,000 / 1,000,000) * 1,000 = 20
– CDR: (10,000 / 1,000,000) * 1,000 = 10
– RNI: (20 – 10) / 10 = 1.0%
– Doubling Time: 70 / 1.0 = 70 years.