Sectoral distribution of the Gross Domestic Product (GDP) index is primarily used to measure which aspect of a country's progress?

Introduction / Context:
The sectoral distribution of GDP tells us how much different sectors such as agriculture, industry and services contribute to the overall economic output of a country. This distribution is a widely used indicator in development economics, because it shows structural changes in the economy over time. As countries develop, the share of agriculture typically falls while the share of industry and services rises. This question asks which aspect of progress is mainly captured by the sectoral distribution of GDP.

Given Data / Assumptions:
- The focus is on sectoral distribution of GDP, that is the share of primary, secondary and tertiary sectors in total output.
- We must identify whether it measures agriculture development, economic development, social development or socioeconomic development.
- We assume standard use of the GDP concept in economic analysis.

Concept / Approach:
GDP itself is a measure of economic output and growth. When we break GDP into sectors, we can see the structure of production and how it changes with development. A higher share of industry and services and a relatively lower share of agriculture is generally associated with higher levels of economic development. Therefore the sectoral distribution of GDP is primarily an indicator of economic development and structural transformation, though it also has implications for social and socioeconomic aspects.

Step-by-Step Solution:
Step 1: Recognise that GDP is an economic measure, expressing the value of all final goods and services produced in an economy in a given period. Step 2: Sectoral distribution of GDP refers to how this total is divided among agriculture, industry and services. Step 3: As economies develop, the share of agriculture usually declines while industry and then services become dominant. This pattern is a classic indicator of economic development. Step 4: Although agriculture development is related, looking only at the share of agriculture does not capture the whole picture; the distribution across all sectors reflects broader economic development. Step 5: Social development involves factors like education, health and gender equality, which are not directly measured by GDP shares, so it is not the primary focus here. Step 6: Therefore, the best description is that sectoral distribution of GDP measures the economic development of a country.

Verification / Alternative check:
Consider two hypothetical countries. Country A has 60% of GDP from agriculture, 20% from industry and 20% from services. Country B has 10% from agriculture, 30% from industry and 60% from services. Most economists would say Country B is more economically developed due to its larger industrial and service sectors. This judgement is based directly on sectoral distribution of GDP, confirming that the index is a tool for examining economic development rather than only agriculture or purely social progress.

Why Other Options Are Wrong:
Agriculture development of a country is wrong because sectoral distribution covers all sectors, not just agriculture, and development is not judged solely by the agriculture share.
Social development of a country is wrong because although economic structure influences society, social development is typically measured by indicators like literacy, life expectancy and health, not directly by GDP sector shares.
Socioeconomic development of a country is broader and includes both economic and social dimensions, whereas sectoral distribution of GDP focuses more specifically on the economic production structure, so economic development is the more precise answer in this context.

Common Pitfalls:
Students sometimes mix up economic and social indicators, assuming that any index related to GDP must also fully capture social development. While there is a relationship, they are not the same. Another confusion arises when learners focus only on agriculture, thinking that increasing its share always means development, but in most development patterns the opposite is true. Remembering the typical shift from primary to secondary and tertiary sectors as income rises can help in correctly interpreting sectoral GDP data.

Final Answer:
Sectoral distribution of the GDP index is primarily used to measure the economic development of a country.