Crude Death Rate in AP Human Geography

Turning a death count into CDR, then into growth

The formula is deaths in a year divided by total population, times 1,000. A country of 10 million with 80,000 deaths in a year has a CDR of 8 per 1,000.

CDR matters in this course because mortality is one of the three forces, along with fertility and migration, that decide whether a population grows or shrinks. That's the core question of Unit 2 (Population and Migration), Topic 2.4 (Population Dynamics). Geographers explain growth with the rate of natural increase (RNI) and doubling time, and both start with CDR.

Here's the chain. Say a country has a CBR of 30 and a CDR of 16 per 1,000. RNI is 30 minus 16, which is 14 per 1,000, or 1.4%. If net migration is zero, you can approximate doubling time as 70 divided by the RNI percentage (the Rule of 70), so 70 ÷ 1.4 gives roughly 50 years. Otherwise, use the annual population growth rate, including net migration.

The exam doesn't allow calculators, so get comfortable with this mental math. Remember to convert "per 1,000" to a percent by dividing by 10 before you use the Rule of 70. Natural increase leaves out migration, so a country can have a positive RNI and still lose people if enough of them emigrate.

Why an aging, wealthy country can post a high CDR

Since CDR ignores age, it often tracks age structure more than health care quality. Japan has excellent health care and very long life expectancy, but its CDR is higher than those of many lower-income countries in sub-Saharan Africa. Japan has a large elderly population, and old people die at higher rates even when they're well cared for. A country where most people are young has fewer deaths per 1,000 simply because fewer people are near the end of life.

This is where CDR ties into Topic 2.3 (Population Composition). A population pyramid with a wide top and a narrow base predicts a rising CDR. A pyramid with a wide base predicts a lower one, as long as basic health care keeps child deaths down. If a population pyramid appears next to a death rate, use its shape to explain the number.

What pushes death rates up or down

Topic 2.4 (Population Dynamics) asks you to explain mortality with social, cultural, political, and economic factors. These usually fall into a few groups:

• Economic: clean water, sanitation, food supply, and access to hospitals and vaccines
• Political: war, government health spending, and public health campaigns
• Social and cultural: education levels (especially for women), diet, and attitudes toward medical care

In the demographic transition model, CDR drops sharply in Stage 2 while birth rates stay high, which is why population grows fast in that stage. In later stages CDR stays low, and in an aging population it can creep back up. The epidemiological transition model explains why, as the main causes of death shift from infectious disease toward chronic and degenerative illness.

Reading CDR in a data table and avoiding the IMR mix-up

A table row reading CBR 30 and CDR 16 gives you an RNI of 14 per 1,000 with one subtraction. When a multiple-choice question lists those rates for several countries, that number lets you rank each country by natural increase or match it to a DTM stage. In the free response, Question 2 (one stimulus) or Question 3 (two stimuli) can give you a data set or population pyramid and ask you to explain a population trend. A strong answer names the rate, does the subtraction, and then explains a specific cause, such as an aging population or improved sanitation.

A common wrong move is treating CDR as a development indicator. A low CDR doesn't prove a country is wealthy, and a high one doesn't prove it's poor. If a question asks which measure best reflects health care quality or development, pick infant mortality rate (deaths of babies under age one per 1,000 live births) or life expectancy. Infant deaths respond directly to sanitation, nutrition, and medical care, and they aren't distorted by a large elderly population the way CDR is.