Methods of Measurement of National Income - Output Method/Product Method

The output method is also called the product method or inventory method. It is used to measure National Income by calculating the value of goods and services produced.

1. Final Goods (Final Product) Approach

• Count only the value of final goods and services produced in the economy.
• Intermediate goods are excluded to prevent double counting.

2. Value-Added Approach

• At each stage of production, only the value added is counted.
• Value Added = Value of Output − Value of Intermediate Inputs.

Example:

Sum of value added at all stages = Value of final product (₹500).

• Farmer produces wheat worth Rs 50, sells to baker.
• Baker produces bread worth Rs 100 using Rs 50 wheat.
• Simple aggregation = Rs 150 (double counting).
• Correct aggregate = Rs 100 (final product only).
• Baker's Value Added = Rs 100 − Rs 50 = Rs 50.

\[\mathrm{GDP}\equiv\sum_{i=1}^N\mathrm{GVA}_i\]

GDP

• GDP = Sum of Gross Value Added over all firms in the economy.

Gross vs Net Value Added

\[GVA_i\equiv Q_i-Z_i\equiv V_i+A_i-Z_i\]

Where:

• \[Q_i\]​ = Value of output of firm \[i\]
• \[Z_i\] = Value of intermediate goods used
• \[V_i\] = Value of final goods sold
• \[A_i\]​ = Addition to inventories

Inventories = Stock of unsold goods, semi-finished goods, or raw materials held by a firm

Change in Inventories = Current year's stock − Previous year's stock.

• Positive change → Inventory accumulation
• Negative change → Inventory decumulation

Changes in inventories can be planned or unplanned.

• Count only final goods; exclude intermediate goods
• Include imputed value of self-consumed goods (e.g., farmer consuming own wheat)
• Adjust for indirect taxes and subsidies
• Account for price changes
• Include exports; exclude imports
• Account for depreciation
• Exclude second-hand goods (they were counted in the year of original production).

• Output Method counts value of all final goods and services produced to measure national income.
• Two approaches: Final Product Approach and Value Added Approach - both yield the same result.
• Value Added at each stage = Output value − Intermediate input value.
• GDP is the sum of Gross Value Added across all firms in the economy.
• Inventories (stock changes) are included in GVA to capture production not yet sold.
• The key precaution is to avoid double counting - count only final goods or use the value-added method.
• Second-hand goods, intermediate goods, and imports are excluded from the calculation.