Question

Define the crude birthrate (CBR) and the crude death rate (CDR). Describe how these rates are used to calculate the percent rate of growth and the doubling time of a population.

Short answer

The crude birthrate (CBR) is the number of live births per 1,000 people in a population in a given year, while the crude death rate (CDR) is the number of deaths per 1,000 people in a population in a given year. The percent rate of growth is calculated by subtracting the CDR from the CBR and dividing by 10. The doubling time, or the time it takes for a population to double, is calculated by dividing 70 by the percent rate of growth.

Step-by-step solution

Define the Crude Birthrate (CBR)

The Crude Birthrate (CBR) is the number of live births per 1,000 people in a population in a given year.

Define the Crude Death Rate (CDR)

The Crude Death Rate (CDR) is the number of deaths per 1,000 people in a population in a given year.

Calculate the percent rate of growth

The percent rate of growth of a population can be calculated by subtracting the CDR from the CBR, dividing the result by 10. This equation can be represented as follows: \[ro = \frac{(CBR - CDR)}{10}\], where ro is the annual growth rate in percent.

Determine the doubling time

To determine the doubling time of a population, the rule of 70 is commonly used. This rule states that to find the number of years it takes for a population to double, divide 70 by the annual growth rate. Mathematically, it is represented as \[Dt = \frac{70}{ro}\], where Dt is the doubling time, and ro is the annual growth rate in percent as calculated in step 3.