In demography, the birth rate of a country is typically defined as which of the following measures?

Introduction / Context:
Demographic indicators such as birth rate, death rate, and fertility rate are used to study the population dynamics of a country. These measures help policymakers understand population growth, design health programmes, and plan for education and employment needs. The birth rate is a specific measure of how many births occur relative to the size of the population. This question tests whether the candidate knows the standard definition used in demography for birth rate.

Given Data / Assumptions:

• The options describe births per 100 persons, per 1000 persons, and births per kilometre of area.
• We assume the conventional international and Indian statistical definition of crude birth rate.
• The reference period is one year.
• The base population is usually the mid year population.

Concept / Approach:
The crude birth rate is defined as the number of live births occurring during a year per 1000 population, usually calculated using the mid year population estimate. This standardises the measure so that countries with different population sizes can be compared. Measuring births per unit of area, such as per square kilometre, would mix population density with fertility, which is not how birth rate is defined. Similarly, a base of 100 persons would be unusual and is not the standard practice in demographic statistics.

Step-by-Step Solution:
Step 1: Recall the standard definition of crude birth rate: number of live births per 1000 population in one year.Step 2: Compare this with option B, which matches exactly: number of births per 1000 persons in one year.Step 3: Option A uses a base of 100 persons, which is not standard in demography; most demographic rates are expressed per 1000 population.Step 4: Options C and D define birth rate per kilometre or per 100 kilometres of area, which relate more to population density rather than fertility.Step 5: Therefore, the correct definition among the options is births per 1000 persons in one year.

Verification / Alternative check:
Demography textbooks and United Nations statistical manuals consistently define crude birth rate as the number of live births per 1000 population in a given year. National statistical agencies, including those in India, publish birth rate figures using the same base. The 1000 base makes interpretation easier and allows direct comparison across regions. This standard confirms that option B is the correct answer.

Why Other Options Are Wrong:
Option A (per 100 persons) is incorrect because the usual base is 1000, not 100, for birth rate. Options C and D (per kilometre of area or per 100 kilometres of area) mix geographic area with population dynamics and are not used in standard demographic practice to describe birth rate; they would reflect a combination of fertility and population density. Thus, only option B matches the accepted definition.

Common Pitfalls:
Students may confuse birth rate with population density, which is measured as people per square kilometre. They may also generalise from other types of percentages, assuming a base of 100, but demographic indicators traditionally use a base of 1000. Another pitfall is to confuse crude birth rate with total fertility rate, which measures the average number of children born to a woman over her lifetime. Keeping these concepts distinct avoids errors in such questions.

Final Answer:
The birth rate is defined as the Number of births per 1000 persons in one year.