Understanding double deflation: What it does and why it matters

UPSC Syllabus: Gs Paper 3 – Indian economy

Introduction

India’s revised GDP series has brought renewed attention to double deflation as a method for measuring real economic activity. The method separately adjusts output and intermediate consumption for price changes, unlike single deflation. This is important because output and input prices may move differently, affecting real GVA estimates. It also explains why the implicit GVA deflator can move differently from familiar indices such as CPI, WPI and PPI.

Understanding Deflation

1. Current-price value: A nominal value is measured at the prices prevailing in the current period, so it reflects the value of goods and services at those prices.
2. Constant-price value: A real value is measured at the prices of a fixed base period, so the effect of price changes is removed.
3. Meaning of deflation: Deflation is the process of converting nominal values into real values by adjusting them for changes in prices.
4. How deflation works: An appropriate price index is used to adjust a nominal value for price changes and obtain its real or volume value.

Single Deflation and Its Limitations

1. Single Deflation Approach: Single deflation utilizes a single price index to deflate nominal gross value added estimates into constant price figures.
2. Price Movement Assumption: This method assumes that output prices and intermediate input prices move together continuously without any significant divergence.
3. Divergence Vulnerability: Single deflation fails when input and output prices diverge sharply, leading to heavily distorted real growth metrics nationwide.
4. Absence of Input Tracking: The traditional single index framework completely ignores individual price variations occurring within diverse intermediate goods and industrial production supplies.
5. Overestimation Risks: Assuming parallel price movements can artificially inflate national income statistics during periods characterized by highly volatile raw input costs.
6. Data Simplification Errors: Relying on one price index simplifies statistical calculations but introduces substantial measurement errors in volatile macroeconomic environments

Double Deflation: Concept and Measurement

1. Core concept: Double deflation separately adjusts output and intermediate consumption for their respective price changes, removing the assumption that their prices move together.
2. Output deflation: Current-price output is adjusted using an appropriate output price index to obtain real output.
3. Intermediate consumption deflation: Current-price intermediate inputs are separately adjusted using suitable prices for the goods and services used in production.
4. Real GVA calculation: Real GVA is calculated as real output minus real intermediate consumption, giving the volume-based value added.
5. International recognition: The UN System of National Accounts describes real GVA as output in volume terms less intermediate consumption in volume terms, making double deflation internationally recognised.

Data Requirements and Role of Price Indices

1. Need for detailed data: Double deflation needs detailed information on both output and intermediate-use items, making it more data-intensive than single deflation.
2. Inter-industry linkages: An industry’s output can become another industry’s input, such as coal for electricity and manufacturing or cotton yarn for textiles.
3. Role of PPI: Output PPI (Producer Price Index) covers intermediate-use products as well as final-use products, supporting separate deflation of production items and inputs.
4. Item-level mapping: In India, output and input items from the latest Annual Survey of Industries (ASI) data are mapped with item-level PPI, allowing more granular deflation.
5. Sources of estimates: Manufacturing estimates use MCA-21 (Ministry of Corporate Affairs database) for private corporations, annual reports for public corporations, and ASUSE (Annual Survey of Unincorporated Sector Enterprises) and PLFS (Periodic Labour Force Survey) for the unincorporated sector.

Concerns and Challenges in Double Deflation

1. Data availability: Detailed and timely output and input data are difficult to obtain across all sectors, limiting wider application of double deflation.
2. Changing input structures: Input baskets can change because of technology, imports, quality changes and shifts in sourcing patterns, affecting price measurement.
3. Input-mapping difficulties: Correctly matching input items with suitable price indices is difficult, especially where industries use diverse production inputs.
4. Sectoral coverage: Services and sectors lacking suitable producer-price information create additional difficulties in applying double deflation consistently.
5. PPI limitations: PPI requires adequate coverage, reliable data, updated weights and changing production information to remain useful for national-accounting purposes.

Benefits and Significance of Double Deflation

1. Better volume measurement: Separately deflating output and intermediate consumption gives a more realistic measure of underlying production volumes.
2. Captures relative prices: The method directly captures differences between output-price and input-price movements, which single deflation can miss.
3. Improves GVA estimates: It provides a better measure of real GVA when input prices and output prices move in different directions.
4. International comparability: Double deflation is used for industry-level volume GVA estimation in countries and regions including the US, Japan, UK, Canada, Australia and Eurozone.
5. Better statistical framework: Richer survey, administrative and price data allow national accounts to measure real economic activity with greater detail and consistency.

India’s Approach under the Revised GDP Series

1. Use in the new GDP series: The revised GDP series uses double deflation for agriculture and manufacturing, while volume extrapolation is used for the remaining sectors.
2. Manufacturing focus: Manufacturing has detailed double-deflation estimates because of its input-intensive nature and the availability of rich ASI and price data.
3. Extent of application: Of 30 manufacturing compilation categories, double deflation is applied to 28 categories broadly corresponding to combinations of two- and three-digit NIC industries.
4. Exceptions: Food products and pharmaceutical products use volume extrapolation because of difficulties in mapping their input items.
5. Move towards PPI: The move towards PPI is important because its greater granularity and coverage can better match the valuation principles used in national accounts.
6. Implicit GVA deflator: The implicit GVA deflator is a measure of the overall price change reflected in GVA, calculated as Nominal GVA ÷ Real GVA × 100.
7. Why it behaves differently: Under double deflation, output and intermediate consumption are deflated separately, so the implicit GVA deflator depends on their relative price movements and weights, rather than on one directly observed GVA price index.
8. Why it can decline: If input prices rise faster than output prices, real GVA can grow faster than nominal GVA, causing the implicit GVA deflator or its growth rate to decline even when CPI, WPI or PPI are rising.
9. Why CPI or WPI cannot replace it: CPI, WPI and PPI have different coverage and weights, so nominal GDP growth minus CPI or WPI inflation does not necessarily give real GDP growth.

Conclusion

Double deflation improves the measurement of real economic activity by separately accounting for output and input price movements. Its results may differ from CPI or WPI because the implicit GVA deflator emerges from the national-accounts calculation. Its effectiveness therefore depends on detailed, appropriate and consistent data, making better price and input information central to improving GDP measurement.

Question for practice:

Examine the concept of double deflation, its significance in measuring real GVA, and its application in India’s revised GDP series.

Source: Business Standard ; Financial Express