Interest Rate Parity and Purchasing Power Parity: Theory, Indian Evidence, and Corporate Implications
Executive summary
This article explains the theories of Interest Rate Parity (IRP) and Purchasing Power Parity (PPP) and evaluates how well they describe exchange-rate behaviour in India. It covers:
- The formal statements of Covered and Uncovered Interest Rate Parity (CIRP and UIRP) and Absolute/Relative PPP.
- The economic intuition behind the relationships and the conditions under which each holds.
- Numerical illustrations (digit-by-digit calculations) showing how IRP implies forward rates from observed spot and interest-rate differentials — with India–US short-term data (August 2025).
- Empirical and institutional reasons why the parity relationships may systematically deviate in India: capital controls, transaction costs, risk premia, market segmentation, central bank intervention, and differing speeds of price adjustment.
- Corporate case studies and practical hedging examples for Indian exporters and importers, showing how firms apply or fail to obtain parity outcomes in practice.
- Policy implications and actionable guidance for Indian corporates and financial managers (risk management, hedging strategy, accounting treatment) and for policymakers.
- Key empirical facts used in the article (August 2025): the RBI policy repo rate is 5.50%; the 3-month Indian T-bill yield is about 5.46% (annualised); the 3-month US Treasury bill yield is about 4.32% (annualised); and USD/INR spot trades near ₹87.33 per US dollar. These data points are from RBI/market sources and public bond-rate series.
1. Introduction — why parity matters for accountants and bankers
Interest-rate and purchasing-power relationships are foundational concepts linking monetary variables, asset prices, and exchange rates. For practitioners—chartered accountants, treasury managers, and bankers—these theories are critical because they inform:
How to price forward contracts and cross-currency funding.
Expectations about currency depreciation/appreciation and its translation into financial statements.
Hedging decisions, accounting for currency risk under Ind AS/IFRS, and the valuation of foreign-currency cash flows.
While the theories present elegant arbitrage-free relationships, real-world departures are common and economically meaningful. This article focuses on how the theories work in practice for India and what Indian firms should do about deviations.
2. Interest Rate Parity (IRP): definitions and intuition
2.1 Covered Interest Rate Parity (CIRP)
Statement (discrete, one-period):
For two currencies (domestic = INR, foreign = USD), covered interest rate parity states that the forward exchange rate
F
F must satisfy:
F=S×1+i
domestic 1+i
foreign
F=S× 1+i
foreign
1+i
domestic
where:
S S is the current spot exchange rate (domestic currency per unit of foreign currency; here ₹/USD),
i domestic i domestic
and i
foreign i foreign
are the domestic and foreign interest rates for the same maturity,
F
F is the forward exchange rate for the same maturity.
Intuition: If the forward rate differed from this relationship, an arbitrageur could borrow in the cheaper currency, convert at spot, invest in the higher-yielding currency, and lock in a forward contract to convert back — earning a riskless profit. In modern interbank FX markets where forward contracts are liquid and counterparty risk is manageable, CIRP tends to hold very tightly for covered transactions between major banks and currencies (modulo credit/settlement risk).
2.2 Uncovered Interest Rate Parity (UIRP)
Statement:
UIRP links expected spot exchange-rate movements to interest differentials:
E[St+1]≈St×1+i
domestic1+i foreign E [St+1]≈St×1+i foreign 1+i
domestic
or in growth/approximate form:
E(ΔSS)≈i domestic −i
foreign E(SΔS)≈i domestic −i
foreign
Intuition: Investors are indifferent between investing in domestic currency assets or foreign currency assets if the expected change in the exchange rate offsets yield differentials. Unlike CIRP, UIRP is an ex-ante, risk-bearing statement: it requires expectations about future spot rates and assumes risk neutrality (or exactly offsetting risk premia).
Key difference: CIRP is an arbitrage (no-arbitrage) relationship enforceable by covered positions; UIRP is a statement about expected returns and hence more fragile empirically because it depends on risk premia and expectations.
3. Numerical illustration — IRP between USD and INR (three-month horizon)
We now demonstrate CIRP numerically using market observations for August 2025. The arithmetic is shown step by step.
Data (observed):
Spot USD/INRS=87.331
S=87.331 ₹ per USD.
Wise 3-month Indian T-bill yield (annualised)
i
INR, annual=5.46%
i
INR, annual =5.46%.
Investing.com 3-month US Treasury bill yield (annualised)
i
USD, annual =4.32%
i
USD, annual=4.32%.
FRED
Step 1: convert annual yields to a 3-month period (quarterly)
Domestic quarterly rate
i
INR,3m=5.46%×312=5.46%×0.25=1.365%
i
INR,3m=5.46%×123=5.46%×0.25=1.365%.
Calculation (digit by digit):
0.0546×0.25=0.01365=1.365%0.0546×0.25=0.01365=1.365%.
Foreign quarterly rate
USD,3m=4.32%×312=4.32%×0.25=1.08%i
USD,3m=4.32%×123=4.32%×0.25=1.08%.
Calculation: 0.0432×0.25=0.0108=1.08%0.0432×0.25=0.0108=1.08%.
Step 2: apply CIRP formula for the 3-month forward rate
F3mF3mF3m=S×1+iINR,3m1+iUSD,3mF3m=S×1+iUSD,3m1+i
INR,3m
Plug values:
F3m=87.331×1+0.013651+0.0108
F3m=87.331×1+0.01081+0.01365
Compute numerator and denominator:
Numerator:
1+0.01365=1.013651+0.01365=1.01365.
Denominator:
1+0.0108=1.01081+0.0108=1.0108.
Now compute the fraction:
Fraction
=1.013651.0108=1.0108 1.01365
Compute the fraction digit-by-digit (division):
1.01365÷1.0108≈1.002806 1.01365÷1.0108≈1.002806 (rounded to six decimal places).
Finally:
F3m=87.331×1.002806≈87.577234F3m=87.331×1.002806≈87.577234
Thus, the implied 3-month forward USD/INR ≈ ₹87.5772 per USD. (This implies a 3-month rupee depreciation vs spot of
87.5772−87.331=0.2462
87.5772−87.331=0.2462 paise, which is a 0.2808% change over three months. Annualised this is ≈ 1.12% — roughly equal to the annual interest differential of 1.14% = (5.46% − 4.32%).) The close numerical equality illustrates the core of CIRP: the forward premium equals the interest differential (after annualisation).
Investing.com
FRED
Wise
Interpretation: Covered arbitrage implies that the forward market prices a slight INR depreciation over three months because Indian short rates are higher than US short rates. The forward market therefore offsets higher INR yields by a forward depreciation of the INR, keeping covered returns equal.
4. From CIRP to corporate action: a hedging example
Case: Mid-sized Indian IT exporter (example)
Context: An Indian IT firm, IndoSoft Pvt. Ltd., expects USD 10 million receivable in 3 months from a US client. Management wants to decide between (A) leaving exposure unhedged (UIRP implicit bet) or (B) hedging via a 3-month forward contract.
Priced forward (from CIRP): ₹87.5772 per USD.
If the firm hedges: guaranteed INR receipts = USD 10,000,000 × ₹87.5772 = ₹875,772,000.
Unhedged (exposure to future spot): If the firm leaves exposure unhedged, the rupee could appreciate or depreciate. Suppose management’s expected future spot (subjective) is ₹86.50 (they expect mild appreciation). If realized, receipts = ₹865,000,000 (USD 10m × 86.50), which is ₹10.772m less than the forward-hedged amount. Conversely, if spot depreciates to ₹89.00, receipts = ₹890,000,000, which is ₹14.228m more than hedged.
Decision drivers for the firm:
Risk tolerance and cash-flow certainty: A bank-funded balance sheet or upcoming INR liabilities may make a firm favour hedging.
Opportunity cost: If firm expects rupee appreciation beyond forward-implied appreciation, leaving exposure unhedged could increase INR receipts, but this is speculation against the forward curve (which integrates market expectations and risk premia).
Accounting: Hedge accounting under Ind AS requires documentation and effectiveness testing; the firm must weigh P&L volatility vs hedge accounting complexity.
Practical note: The forward rate used by the firm will include bank margin and credit considerations; small deviations from theoretical CIRP may exist for corporates vs interbank forwards.
5. Uncovered IRP (UIRP): empirical reliability and risk premia
UIRP posits that expected depreciation equals the interest differential. Empirically, UIRP performs poorly at short to medium horizons in cross-sectional studies: currencies with higher interest rates tend to appreciate ex-post rather than depreciate — the so-called forward bias or “forward premium puzzle.” Two important reasons:
Risk premia: Investors demand compensation for bearing currency risk. If high-yield currencies are riskier, they may command higher expected returns, violating the simple UIRP equality.
Time-varying expected returns and slow adjustment of expectations: Expectations about future fundamentals (monetary policy, growth, current account) shift and may not equal interest differentials.
Indian context: India often exhibits a positive carry for rupee positions over certain short windows; empirical UIRP failure is common. Foreign investors in Indian assets also face regulatory and settlement considerations that affect expected returns.
6. Purchasing Power Parity (PPP): definitions and theory
6.1 Absolute PPP
Absolute PPP states that identical baskets of goods cost the same across countries when measured in a common currency:
S= P domestic
P foreign S=
P foreign
P domestic
Where PP denotes price levels.
6.2 Relative PPP
Relative PPP focuses on inflation rates and exchange-rate changes:
ΔSS≈πdomestic−πforeignSΔS≈π domestic −πforeign whereπ
π denotes the inflation rate. Over time, a country with higher inflation should see its currency depreciate approximately by the inflation differential.
Intuition: If domestic prices rise faster, domestic currency buys less goods, and the exchange rate must adjust to restore purchasing power parity.
7. PPP numerical illustration — India vs US (July 2025)
Observed short-run inflation (annualised, year-on-year, July 2025):
India headline CPI ≈ 1.55% (July 2025).
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United States headline CPI ≈ 2.7–2.8% (July 2025).
Trading Economics
Bureau of Labor Statistics
According to relative PPP, the expected annual change in USD/INR would be:
Expected annual % change in USD/INR≈πINR−πUSD
Expected annual % change in USD/INR≈πINR−πUSD
Plugging numbers: 1.55%−2.75%≈−1.20%
1.55%−2.75%≈−1.20% per year — i.e., PPP suggests a modest rupee appreciation versus the dollar (because India’s inflation has been lower than the US in this snapshot).
Reality check: In 2025 year-to-date, USD/INR traded around mid-80s–high-80s, and exchange-rate moves reflect not only inflation differentials but also capital flows, policy surprises, and risk appetite. PPP is a long-run anchor; short-term deviations can be large and persistent.
Stylised conclusion: In July–August 2025, the inflation differential pointed towards a modest rupee appreciation on PPP grounds, but markets priced a near-term small rupee depreciation via forward rates (driven by interest differentials and other factors). This highlights different time horizons and drivers for PPP and IRP.
Trading Economics +1
8. Why parity relationships deviate in India (institutional and empirical factors)
Even when parity relationships are theoretically neat, practical deviations in India arise from several sources:
8.1 Capital controls, regulatory segmentation, and trading limits
India’s capital account is not fully liberalised. While investment inflows (portfolio and FDI) are substantial, certain capital movements face regulatory ceilings, approvals, or limits on derivatives use for corporates. These frictions reduce arbitrage activity that would otherwise enforce parity exactly.
8.2 Transaction costs, bid–ask spreads, and taxes
Bid–ask spreads in offshore and onshore forwards, stamp duties, market fees, and tax rules for derivatives and interest income create wedges that can prevent clean arbitrage.
8.3 Credit and settlement risk (counterparty considerations)
CIRP holds tightly for large internationally active banks because they can both borrow and lend in multiple currencies and can back forward positions with collateral. Smaller corporates and local banks face higher credit costs and may receive different forward quotes from their relationship bank.
8.4 Country risk premium and political risk
Emerging-market currencies often carry a country risk premium. During episodes of stress (global risk-off, geopolitical shocks), the rupee may depreciate beyond what interest or inflation differentials justify because investors demand an extra premium for holding INR assets.
8.5 Central bank intervention and FX reserves policy
The Reserve Bank of India (RBI) intervenes in FX markets to ensure orderly movement and dampen excessive volatility. Active intervention (spot/forward purchases or sales, FX swaps) can push spot/forward away from parity-implied levels temporarily.
8.6 Differences in tradables/non-tradables inflation (Balassa–Samuelson effect)
PPP assumes similar baskets and factor price equalisation. In reality, non-tradable prices (services, wages) and productivity differences matter. For India, services have different inflation dynamics relative to goods, which weakens short-run PPP.
9. Corporate case studies: real examples and numerical illustrations
To illustrate how parity theories play out in practice for Indian firms, we present two stylised but realistic case studies.
9.1 Case A — An Indian importer of capital goods (manufacturing)
Firm: Rajasthan Machinery Ltd. expects to pay USD 2 million for imported machinery in 6 months. The firm operates with thin margins and significant INR liabilities (wages, local suppliers).
Options:
Hedge with forward (locked rate) — eliminates FX risk.
Invoice in INR (supplier accepts) — shifts exchange risk to supplier (not always possible).
Natural hedge — match FX inflows and outflows, not available here.
Leave unhedged — speculate or accept risk.
Numerical illustration: Using an approximate 6-month version of CIRP (extend the previous method to 6 months using semiannualised rates), the firm compares hedged cost vs expected cost.
Suppose:
Spot = ₹87.331.
6-month INR yield ≈ 5.46% × 0.5 = 2.73% (approx).
6-month USD yield ≈ 4.32% × 0.5 = 2.16% (approx).
Implied 6-month forward:
F6m=87.331×1+0.02731+0.0216≈87.331×1.005582≈87.817F6m=87.331×1+0.02161+0.0273≈87.331×1.005582≈87.817
Hedged payables = USD 2m × 87.817 = ₹175,634,000.
If firm remains unhedged and spot moves favourably to ₹86.00, it pays ₹172,000,000 — ₹3.634m less. If spot moves unfavourably to ₹90.00, it pays ₹180m — ₹4.366m more. Management must weigh volatility vs expected moves and cost of capital.
Accounting: If hedged with a derivative and hedge accounting applied, profit volatility can be managed but documentation and effectiveness need to be maintained as per Ind AS 109.
9.2 Case B — An Indian exporter and the role of the forward market
Firm: Jaipur Textiles Ltd. receives USD 5m in 3 months. Management wants INR visibility for wage payments.
If forward = ₹87.5772 (3-month) then hedged receipts are ₹437,886,000. If the company leaves exposure unhedged and rupee appreciates to ₹86.00, it would receive ₹430,000,000 — lower than hedged. The hedging premium (difference) is insurance against appreciation.
Strategic choice: Many exporters prefer to hedge a portion (e.g., 60–80%), keeping some exposure to potential favourable currency swings while locking in a predictable base line.
Operational note: Hedging costs reflect not only forward points but also bank margins; large exporters often obtain better forward pricing from competitive tendering among banks.
10. Empirical evidence for India — what the data shows
Several stylised empirical points about India:
CIRP holds closely in the interbank market for short maturities, i.e., bank-to-bank forward pricing closely reflects interest differentials once transaction costs and credit are accounted for. For corporates, small deviations occur due to spreads and credit costs. (See 3-month forward example above.)
Investing.com
FRED
UIRP weak or unreliable in the short run. Empirical tests over decades show that expected depreciation does not systematically offset interest differentials — investors have earned excess returns (carry) at times or suffered losses during stress episodes.
PPP is a long-run relationship; in the short-run India deviates substantially. Price levels and consumption baskets differ, and tradables vs non-tradables produce persistent PPP deviations.
Inflation differentials in 2025 suggested a modest rupee appreciation (India inflation lower than US in mid-2025), yet forwards and spot were influenced by capital flows, tariffs and geopolitical events, leading to different short-term outcomes.
Trading Economics +1
11. Special episodes and Indian realities
11.1 2013 taper tantrum and FX behaviour (brief lesson)
During the 2013 US taper episode, emerging markets including India experienced capital outflows and sharp currency depreciation. Even if PPP/IRP suggested different medium-term paths, sudden stops of capital flows caused large deviations. Central banks (including RBI) often use FX reserves or monetary policy to stabilise markets.
Lesson for present: Policy or geopolitical shocks can overwhelm parity relationships in the short run.
11.2 Recent (2025) considerations: tariffs and global policy
In August 2025, global trade tensions (tariffs) and central-bank stance created uncertainty. RBI kept repo at 5.50% in August 2025 citing inflation moderation but cautious on external shocks; forward/spot pricing incorporated these risks. These developments feed directly into forward pricing and expected exchange-rate dynamics.
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Reuters
12. Practical guidance for Indian corporates, treasurers, and accountants
12.1 When to rely on CIRP vs UIRP vs PPP
CIRP: Use when pricing/valuing forward contracts and executing covered positions. For pricing forwards, use market-determined forward rates (CIRP provides the theoretical anchor). For accounting and treasury control, assume CIRP holds for interbank pricing but bank quotes include spreads.
UIRP: Do not rely on UIRP to forecast future spot reliably. Use it as a theoretical benchmark; however, incorporate explicit risk premia and scenario analysis rather than blind forecasting.
PPP: Use as a long-run valuation anchor (e.g., for strategic planning, valuation models extending 5–10 years), but not as a short-term forecast tool.
12.2 Hedging policy (recommended practices)
Set a written FX policy: specify exposures, hedge ratios, allowed instruments, authorized counterparties, and reporting frequency.
Hedge proportionally to cash-flow certainty: predictable receivables/payables warrant higher hedge ratios.
Use natural hedges where possible: match foreign-currency revenues and foreign-currency liabilities.
Consider options vs forwards: options provide asymmetric payoff (costly premium) but protect against adverse moves while allowing upside.
Account and documentation: ensure hedge documentation for Ind AS/IFRS hedge accounting to manage reported P&L volatility.
12.3 Pricing and transfer pricing
Firms
Interest Rate Parity and Purchasing Power Parity: Theory, Indian Evidence, and Corporate Implications
Author: Rahul Sharma, FCA, MBA (Fin), LLB, CAIIB — Chartered Accountant, UCO Bank, Jaipur, Rajasthan, India
Executive summary
This article explains the theories of Interest Rate Parity (IRP) and Purchasing Power Parity (PPP) and evaluates how well they describe exchange-rate behaviour in India. It covers:
The formal statements of Covered and Uncovered Interest Rate Parity (CIRP and UIRP) and Absolute/Relative PPP.
The economic intuition behind the relationships and the conditions under which each holds.
Numerical illustrations (digit-by-digit calculations) showing how IRP implies forward rates from observed spot and interest-rate differentials — with India–US short-term data (August 2025).
Empirical and institutional reasons why the parity relationships may systematically deviate in India: capital controls, transaction costs, risk premia, market segmentation, central bank intervention, and differing speeds of price adjustment.
Corporate case studies and practical hedging examples for Indian exporters and importers, showing how firms apply or fail to obtain parity outcomes in practice.
Policy implications and actionable guidance for Indian corporates and financial managers (risk management, hedging strategy, accounting treatment) and for policymakers.
Key empirical facts used in the article (August 2025): the RBI policy repo rate is 5.50%; the 3-month Indian T-bill yield is about 5.46% (annualised); the 3-month US Treasury bill yield is about 4.32% (annualised); and USD/INR spot trades near ₹87.33 per US dollar. These data points are from RBI/market sources and public bond-rate series.
Trading Economics
Investing.com
FRED
Wise
1. Introduction — why parity matters for accountants and bankers
Interest-rate and purchasing-power relationships are foundational concepts linking monetary variables, asset prices, and exchange rates. For practitioners—chartered accountants, treasury managers, and bankers—these theories are critical because they inform:
How to price forward contracts and cross-currency funding.
Expectations about currency depreciation/appreciation and its translation into financial statements.
Hedging decisions, accounting for currency risk under Ind AS/IFRS, and the valuation of foreign-currency cash flows.
While the theories present elegant arbitrage-free relationships, real-world departures are common and economically meaningful. This article focuses on how the theories work in practice for India and what Indian firms should do about deviations.
2. Interest Rate Parity (IRP): definitions and intuition
2.1 Covered Interest Rate Parity (CIRP)
Statement (discrete, one-period):
For two currencies (domestic = INR, foreign = USD), covered interest rate parity states that the forward exchange rate F F must satisfy:
F=S×1+idomestic1+iforeignF=S×1+iforeign 1+idomestic
where:
S S is the current spot exchange rate (domestic currency per unit of foreign currency; here ₹/USD), i domestic i domestic and i foreign i foreign are the domestic and foreign interest rates for the same maturity,
F F is the forward exchange rate for the same maturity.
Intuition: If the forward rate differed from this relationship, an arbitrageur could borrow in the cheaper currency, convert at spot, invest in the higher-yielding currency, and lock in a forward contract to convert back — earning a riskless profit. In modern interbank FX markets where forward contracts are liquid and counterparty risk is manageable, CIRP tends to hold very tightly for covered transactions between major banks and currencies (modulo credit/settlement risk).
2.2 Uncovered Interest Rate Parity (UIRP)
Statement:
UIRP links expected spot exchange-rate movements to interest differentials:
E[St+1]≈St×1+i
domestic 1+iforeignE[St+1]≈St×1+iforeign1+idomestic
or in growth/approximate form: E(ΔSS)≈idomestic−iforeignE(SΔS)≈idomestic−iforeign
Intuition: Investors are indifferent between investing in domestic currency assets or foreign currency assets if the expected change in the exchange rate offsets yield differentials. Unlike CIRP, UIRP is an ex-ante, risk-bearing statement: it requires expectations about future spot rates and assumes risk neutrality (or exactly offsetting risk premia).
Key difference: CIRP is an arbitrage (no-arbitrage) relationship enforceable by covered positions; UIRP is a statement about expected returns and hence more fragile empirically because it depends on risk premia and expectations.
3. Numerical illustration — IRP between USD and INR (three-month horizon)We now demonstrate CIRP numerically using market observations for August 2025. The arithmetic is shown step by step.
Data (observed):
Spot USD/INRS=87.331S=87.331 ₹ per USD.Wise
3-month Indian T-bill yield (annualised) i
INR,annual=5.46%iINR,annual=5.46%.Investing.com
3-month US Treasury bill yield (annualised)
i USD,annual =4.32%iUSD,annual=4.32%.FRED
Step 1: convert annual yields to a 3-month period (quarterly)
Domestic quarterly ratei
INR,3m=5.46%×312=5.46%×0.25=1.365%i
INR,3m=5.46%×123=5.46%×0.25=1.365%.
Calculation (digit by digit):0.0546×0.25=0.01365
=1.365%0.0546×0.25=0.01365=1.365%.
Foreign quarterly rate
iUSD,3m=4.32%×312=4.32%×0.25=1.08%iUSD,3m=4.32%×123=4.32%×0.25=1.08%.
Calculation:0.0432×0.25=0.0108=1.08%0.0432×0.25=0.0108=1.08%.
Step 2: apply CIRP formula for the 3-month forward rate
F3mF3mF3m=S×1+iINR,3m1+i
USD,3m F3m=S×1+iUSD,3m1+iINR,3m
Plug values:
F3m=87.331×1+0.013651+0.0108F3m=87.331×1+0.01081+0.01365
Compute numerator and denominator:
Numerator: 1+0.01365=1.013651+0.01365=1.01365.
Denominator:1+0.0108=1.01081+0.0108=1.0108.
Now compute the fraction:
Fraction=1.013651.0108=1.01081.01365
Compute the fraction digit-by-digit (division):1.01365÷1.0108≈1.0028061.01365÷1.0108≈1.002806 (rounded to six decimal places).
Finally: F3m=87.331×1.002806≈87.577234F3m=87.331×1.002806≈87.577234
Thus, the implied 3-month forward USD/INR ≈ ₹87.5772 per USD. (This implies a 3-month rupee depreciation vs spot of 87.5772−87.331=0.2462
87.5772−87.331=0.2462 paise, which is a 0.2808% change over three months. Annualised this is ≈ 1.12% — roughly equal to the annual interest differential of 1.14% = (5.46% − 4.32%).) The close numerical equality illustrates the core of CIRP: the forward premium equals the interest differential (after annualisation).
Investing.com
FRED
Wise
Interpretation: Covered arbitrage implies that the forward market prices a slight INR depreciation over three months because Indian short rates are higher than US short rates. The forward market therefore offsets higher INR yields by a forward depreciation of the INR, keeping covered returns equal.
4. From CIRP to corporate action: a hedging example
Case: Mid-sized Indian IT exporter (example)
Context: An Indian IT firm, IndoSoft Pvt. Ltd., expects USD 10 million receivable in 3 months from a US client. Management wants to decide between (A) leaving exposure unhedged (UIRP implicit bet) or (B) hedging via a 3-month forward contract.
Priced forward (from CIRP): ₹87.5772 per USD.
If the firm hedges: guaranteed INR receipts = USD 10,000,000 × ₹87.5772 = ₹875,772,000.
Unhedged (exposure to future spot): If the firm leaves exposure unhedged, the rupee could appreciate or depreciate. Suppose management’s expected future spot (subjective) is ₹86.50 (they expect mild appreciation). If realized, receipts = ₹865,000,000 (USD 10m × 86.50), which is ₹10.772m less than the forward-hedged amount. Conversely, if spot depreciates to ₹89.00, receipts = ₹890,000,000, which is ₹14.228m more than hedged.
Decision drivers for the firm:
Risk tolerance and cash-flow certainty: A bank-funded balance sheet or upcoming INR liabilities may make a firm favour hedging.
Opportunity cost: If firm expects rupee appreciation beyond forward-implied appreciation, leaving exposure unhedged could increase INR receipts, but this is speculation against the forward curve (which integrates market expectations and risk premia).
Accounting: Hedge accounting under Ind AS requires documentation and effectiveness testing; the firm must weigh P&L volatility vs hedge accounting complexity.
Practical note: The forward rate used by the firm will include bank margin and credit considerations; small deviations from theoretical CIRP may exist for corporates vs interbank forwards.
5. Uncovered IRP (UIRP): empirical reliability and risk premia
UIRP posits that expected depreciation equals the interest differential. Empirically, UIRP performs poorly at short to medium horizons in cross-sectional studies: currencies with higher interest rates tend to appreciate ex-post rather than depreciate — the so-called forward bias or “forward premium puzzle.” Two important reasons:
Risk premia: Investors demand compensation for bearing currency risk. If high-yield currencies are riskier, they may command higher expected returns, violating the simple UIRP equality.
Time-varying expected returns and slow adjustment of expectations: Expectations about future fundamentals (monetary policy, growth, current account) shift and may not equal interest differentials.
Indian context: India often exhibits a positive carry for rupee positions over certain short windows; empirical UIRP failure is common. Foreign investors in Indian assets also face regulatory and settlement considerations that affect expected returns.
6. Purchasing Power Parity (PPP): definitions and theory
6.1 Absolute PPP
Absolute PPP states that identical baskets of goods cost the same across countries when measured in a common currency:
S=P domestic P foreign S=P foreign P domestic
WherePP denotes price levels.
6.2 Relative PPP
Relative PPP focuses on inflation rates and exchange-rate changes:
ΔSS≈πdomestic−πforeignSΔS≈πdomestic−πforeignwhereππ denotes the inflation rate. Over time, a country with higher inflation should see its currency depreciate approximately by the inflation differential.
Intuition: If domestic prices rise faster, domestic currency buys less goods, and the exchange rate must adjust to restore purchasing power parity.
7. PPP numerical illustration — India vs US (July 2025)
Observed short-run inflation (annualised, year-on-year, July 2025):
India headline CPI ≈ 1.55% (July 2025).
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United States headline CPI ≈ 2.7–2.8% (July 2025).
Trading Economics
Bureau of Labor Statistics
According to relative PPP, the expected annual change in USD/INR would be:
Expected annual % change in USD/INR ≈πINR−πUSD
Expected annual % change in USD/INR≈πINR−πUSD
Plugging numbers:1.55 %−2.75%≈−1.20%1.55%−2.75%≈−1.20% per year — i.e.,
PPP suggests a modest rupee appreciation versus the dollar (because India’s inflation has been lower than the US in this snapshot).
Reality check: In 2025 year-to-date, USD/INR traded around mid-80s–high-80s, and exchange-rate moves reflect not only inflation differentials but also capital flows, policy surprises, and risk appetite. PPP is a long-run anchor; short-term deviations can be large and persistent.
Stylised conclusion: In July–August 2025, the inflation differential pointed towards a modest rupee appreciation on PPP grounds, but markets priced a near-term small rupee depreciation via forward rates (driven by interest differentials and other factors). This highlights different time horizons and drivers for PPP and IRP.
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8. Why parity relationships deviate in India (institutional and empirical factors)
Even when parity relationships are theoretically neat, practical deviations in India arise from several sources:
8.1 Capital controls, regulatory segmentation, and trading limits
India’s capital account is not fully liberalised. While investment inflows (portfolio and FDI) are substantial, certain capital movements face regulatory ceilings, approvals, or limits on derivatives use for corporates. These frictions reduce arbitrage activity that would otherwise enforce parity exactly.
8.2 Transaction costs, bid–ask spreads, and taxes
Bid–ask spreads in offshore and onshore forwards, stamp duties, market fees, and tax rules for derivatives and interest income create wedges that can prevent clean arbitrage.
8.3 Credit and settlement risk (counterparty considerations)
CIRP holds tightly for large internationally active banks because they can both borrow and lend in multiple currencies and can back forward positions with collateral. Smaller corporates and local banks face higher credit costs and may receive different forward quotes from their relationship bank.
8.4 Country risk premium and political risk
Emerging-market currencies often carry a country risk premium. During episodes of stress (global risk-off, geopolitical shocks), the rupee may depreciate beyond what interest or inflation differentials justify because investors demand an extra premium for holding INR assets.
8.5 Central bank intervention and FX reserves policy
The Reserve Bank of India (RBI) intervenes in FX markets to ensure orderly movement and dampen excessive volatility. Active intervention (spot/forward purchases or sales, FX swaps) can push spot/forward away from parity-implied levels temporarily.
8.6 Differences in tradables/non-tradables inflation (Balassa–Samuelson effect)
PPP assumes similar baskets and factor price equalisation. In reality, non-tradable prices (services, wages) and productivity differences matter. For India, services have different inflation dynamics relative to goods, which weakens short-run PPP.
9. Corporate case studies: real examples and numerical illustrations
To illustrate how parity theories play out in practice for Indian firms, we present two stylised but realistic case studies.
9.1 Case A — An Indian importer of capital goods (manufacturing)
Firm: Rajasthan Machinery Ltd. expects to pay USD 2 million for imported machinery in 6 months. The firm operates with thin margins and significant INR liabilities (wages, local suppliers).
Options:
Hedge with forward (locked rate) — eliminates FX risk.
Invoice in INR (supplier accepts) — shifts exchange risk to supplier (not always possible).
Natural hedge — match FX inflows and outflows, not available here.
Leave unhedged — speculate or accept risk.
Numerical illustration: Using an approximate 6-month version of CIRP (extend the previous method to 6 months using semiannualised rates), the firm compares hedged cost vs expected cost.
Suppose:
Spot = ₹87.331.
6-month INR yield ≈ 5.46% × 0.5 = 2.73% (approx).
6-month USD yield ≈ 4.32% × 0.5 = 2.16% (approx).
Implied 6-month forward:
F6m=87.331×1+0.02731+0.0216≈87.331×1.005582≈87.817F6m=87.331×1+0.02161+0.0273≈87.331×1.005582≈87.817 Hedged payables = USD 2m × 87.817 = ₹175,634,000.
If firm remains unhedged and spot moves favourably to ₹86.00, it pays ₹172,000,000 — ₹3.634m less. If spot moves unfavourably to ₹90.00, it pays ₹180m — ₹4.366m more. Management must weigh volatility vs expected moves and cost of capital.
Accounting: If hedged with a derivative and hedge accounting applied, profit volatility can be managed but documentation and effectiveness need to be maintained as per Ind AS 109.
9.2 Case B — An Indian exporter and the role of the forward market
Firm: Jaipur Textiles Ltd. receives USD 5m in 3 months. Management wants INR visibility for wage payments.
If forward = ₹87.5772 (3-month) then hedged receipts are ₹437,886,000. If the company leaves exposure unhedged and rupee appreciates to ₹86.00, it would receive ₹430,000,000 — lower than hedged. The hedging premium (difference) is insurance against appreciation.
Strategic choice: Many exporters prefer to hedge a portion (e.g., 60–80%), keeping some exposure to potential favourable currency swings while locking in a predictable base line.
Operational note: Hedging costs reflect not only forward points but also bank margins; large exporters often obtain better forward pricing from competitive tendering among banks.
10. Empirical evidence for India — what the data shows
Several stylised empirical points about India:
CIRP holds closely in the interbank market for short maturities, i.e., bank-to-bank forward pricing closely reflects interest differentials once transaction costs and credit are accounted for. For corporates, small deviations occur due to spreads and credit costs. (See 3-month forward example above.)
Investing.com
FRED
UIRP weak or unreliable in the short run. Empirical tests over decades show that expected depreciation does not systematically offset interest differentials — investors have earned excess returns (carry) at times or suffered losses during stress episodes.
PPP is a long-run relationship; in the short-run India deviates substantially. Price levels and consumption baskets differ, and tradables vs non-tradables produce persistent PPP deviations.
Inflation differentials in 2025 suggested a modest rupee appreciation (India inflation lower than US in mid-2025), yet forwards and spot were influenced by capital flows, tariffs and geopolitical events, leading to different short-term outcomes
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11. Special episodes and Indian realities
11.1 2013 taper tantrum and FX behaviour (brief lesson)
During the 2013 US taper episode, emerging markets including India experienced capital outflows and sharp currency depreciation. Even if PPP/IRP suggested different medium-term paths, sudden stops of capital flows caused large deviations. Central banks (including RBI) often use FX reserves or monetary policy to stabilise markets.
Lesson for present: Policy or geopolitical shocks can overwhelm parity relationships in the short run.
11.2 Recent (2025) considerations: tariffs and global policy
In August 2025, global trade tensions (tariffs) and central-bank stance created uncertainty. RBI kept repo at 5.50% in August 2025 citing inflation moderation but cautious on external shocks; forward/spot pricing incorporated these risks. These developments feed directly into forward pricing and expected exchange-rate dynamics.
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Reuters
12. Practical guidance for Indian corporates, treasurers, and accountants
12.1 When to rely on CIRP vs UIRP vs PPP
CIRP: Use when pricing/valuing forward contracts and executing covered positions. For pricing forwards, use market-determined forward rates (CIRP provides the theoretical anchor). For accounting and treasury control, assume CIRP holds for interbank pricing but bank quotes include spreads.
UIRP: Do not rely on UIRP to forecast future spot reliably. Use it as a theoretical benchmark; however, incorporate explicit risk premia and scenario analysis rather than blind forecasting.
PPP: Use as a long-run valuation anchor (e.g., for strategic planning, valuation models extending 5–10 years), but not as a short-term forecast tool.
12.2 Hedging policy (recommended practices)
Set a written FX policy: specify exposures, hedge ratios, allowed instruments, authorized counterparties, and reporting frequency.
Hedge proportionally to cash-flow certainty: predictable receivables/payables warrant higher hedge ratios.
Use natural hedges where possible: match foreign-currency revenues and foreign-currency liabilities.
Consider options vs forwards: options provide asymmetric payoff (costly premium) but protect against adverse moves while allowing upside.
Account and documentation: ensure hedge documentation for Ind AS/IFRS hedge accounting to manage reported P&L volatility.
12.3 Pricing and transfer pricing
Firms with foreign currency revenues should price contracts considering forward curves and expected hedging costs. Transfer pricing and documentation must reflect arm’s-length pricing of FX arrangements.
12.4 Interest rate differentials and cross-currency funding
For cross-currency borrowing (e.g., raising USD funds and converting to INR), CIRP shows the forward market will price in interest differentials. Borrowing decisions should account for hedging costs implied by forward rates, not just spot exchange rates.
13. Implications for auditors and financial statement preparers
Valuation of FX derivatives: Assess model inputs (spot, forward, discount rates) and ensure they align with market quotes; CIRP provides a consistency check.
Expected foreign-currency cash flows: When using forecasts in impairment tests or valuation (Ind AS 36/Ind AS 113), be careful with exchange-rate assumptions. Avoid using UIRP as a mechanical forecast; use scenario analysis.
Hedge accounting and effectiveness: Maintain contemporaneous documentation for hedging relationships; auditors should test hedge effectiveness and look for behavioural changes that undermine accounting treatment.
14. Policy implications — what RBI and Indian regulators could consider
Deepen hedging markets: Greater liquidity in onshore FX forwards and options reduces transaction costs and makes CIRP applicable for corporates too.
Transparent communication: Clear communication on intervention strategy reduces uncertainty and lowers currency risk premia.
Gradual capital-account liberalisation: Continued liberalisation (with macroprudential safeguards) reduces segmentation and fosters more effective parity arbitrage.
Encourage local currency invoicing: Where feasible, shift to local-currency trade invoicing with careful risk sharing to reduce balance-sheet currency mismatch.
15. Limitations of theory and the role of judgement
Both IRP and PPP assume frictionless markets or stable structures; real markets have frictions, taxes, legal constraints and behavioural components.
Forecasts must incorporate macro expectations, geopolitics, and liquidity considerations.
For accountants and bankers, the role is not to assert a single deterministic path but to quantify risks, document assumptions, and hedge sensibly.
16. Concluding remarks
Interest Rate Parity (especially covered parity) is a robust short-term relation for pricing forward contracts in liquid markets and an essential tool for treasury pricing and arbitrage checks. Purchasing Power Parity is a useful long-run guide to currency valuation but is a weak short-term forecasting device. In India, institutional frictions, capital-flow dynamics, central-bank interventions, and differential prices between tradables and non-tradables cause systematic and persistent deviations from both UIRP and PPP in the short run.
For Indian corporates and financial managers—particularly chartered accountants and treasury officers—best practice is:
Use market-observed forward rates (which embed CIRP and market expectations) when hedging and valuing FX derivatives.
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Treat UIRP and PPP as theoretical anchors; supplement them with scenario analysis and risk premia adjustments.
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Adopt a disciplined hedging policy, ensure Ind AS/IFRS compliance for hedge accounting, and consider the firm’s appetite for speculation vs certainty.
Monitor macro signals — interest-rate differentials, inflation differentials, capital flow indicators, and central bank communication — and update hedges accordingly.
Appendix A — Worked numeric example summary (three-month CIRP)
Spot USD/INR
S
S = 87.331.
Wise
India 3-month yield (annual) = 5.46% → 3-month = 1.365%.
Investing.com
US 3-month yield (annual) = 4.32% → 3-month = 1.08%.
FRED
ForwardF3m=87.331×1.013651.0108≈87.5772F3m=87.331×1.01081.01365≈87.5772 ₹/USD.
Annualised forward premium ≈ 1.12% ≈ (5.46% − 4.32%) = 1.14% (close, allowing for rounding). This equality is the practical reflection of CIRP.
Appendix B — Selected sources and data references
Reserve Bank of India policy and repo-rate commentary (August 2025).
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India 3-month T-bill yields (market series, August 2025).
Investing.com
US 3-month Treasury yields and Fed rates (August 2025).
FRED
Federal Reserve
USD/INR spot and recent history (2025 daily series).
Wise
Yahoo Finance
India CPI (July 2025 provisional).
Trading Economics
Press Information Bureau
US CPI (July 2025 Bureau of Labor Statistics release).
Bureau of Labor Statistics
Big Mac / PPP illustrative indices (The Economist and compendia).
The Economist
World Population Review
Closing note
If you wish, I can convert this article into a formatted MS Word file with your identity block on the top left, include tables with the numerical calculations, and prepare a short slide deck (pptx) summarising the practical steps for a bank treasury or corporate treasury team. Please let me know if you want the Word file (I will prepare it and provide the file directly).
You said:
Comparative study of different contries and holding good of theses theories may be discussed at length. Closed economies and open economies may be discussed
AI said:
Excellent point, Rahul ji. A comparative dimension will make the article much richer and situational, especially when evaluating Interest Rate Parity (IRP) and Purchasing Power Parity (PPP) in different economies. Let me expand Section 8 and add a new comparative analysis section (between countries, closed vs open economies), before I prepare your final 4000-word version in Word.
Comparative Analysis of IRP and PPP Across Economies
1. IRP and PPP in Advanced Open Economies
United States, Euro Area, and Japan
IRP:
In these economies, capital markets are deep, liquid, and open. Covered IRP (CIRP) generally holds almost perfectly because arbitrageurs—banks, hedge funds, corporates—can borrow/lend freely across currencies and use forward contracts without major capital restrictions. For instance:
In New York or London FX markets, deviations from CIRP are usually measured in basis points and quickly arbitraged away.
During the 2008 crisis, small deviations (“cross-currency basis”) did emerge due to credit and liquidity risk, but they narrowed as markets stabilised.
PPP:
Relative PPP tends to hold in the long run but not short run.
Example: Japan has had decades of deflation/low inflation, yet the yen often appreciated beyond what inflation differentials predict (the “yen puzzle”).
US and EU inflation differentials often map better into long-run USD/EUR shifts, but in the short-run, speculative flows and policy shocks dominate.
Implication: In highly open economies, CIRP is a very reliable pricing tool; PPP is a long-term guide but not a forecasting tool.
2. Emerging Market Economies (e.g., India, Brazil, South Africa)
IRP:
CIRP largely holds in interbank markets, but deviations occur for corporates due to:
Higher transaction costs,
Limited access to global liquidity,
Regulatory limits on derivative usage.
Example: In Brazil during crises, capital controls (IOF tax on FX transactions) created significant forward premia not explained by simple interest differentials.
PPP:
Inflation volatility and exchange-rate intervention often break short-run PPP.
India in 2013 (Taper Tantrum): despite moderate inflation differentials, INR depreciated sharply (~20%) due to capital outflows, showing PPP irrelevance in the short term.
South Africa: persistent inflation higher than US, yet ZAR sometimes appreciates due to commodity booms — PPP explains only partial movements.
Implication: In emerging markets, both theories serve as reference points but cannot be taken as absolute. Central bank actions and capital-flow volatility dominate.
3. Closed or Partially Closed Economies (e.g., China, earlier India pre-1991 reforms)
IRP:
In closed economies, where capital account is restricted, CIRP often fails.
Example: China maintains strict capital controls; forward CNY pricing reflects PBoC’s intervention, not just interest differentials.
Pre-1991 India: exchange rate was largely administratively set, not determined by market forces; thus IRP had little operational meaning.
PPP:
With multiple exchange rates or administered pegs, PPP loses relevance because exchange rate is policy-driven rather than inflation-driven.
For China, PPP deviations are persistent; undervaluation debates (like the “China currency manipulation” accusations of 2000s) show PPP not aligning with official exchange rate.
Implication: In closed economies, IRP and PPP are weak tools. Policy dominates, and parity conditions are overridden by government decisions.
4. Comparative Case Studies
Case A: Turkey (open but crisis-prone)
High inflation (over 60% in recent years).
PPP suggests massive lira depreciation, which indeed occurred — but overshooting was far worse due to loss of investor confidence.
IRP deviations occurred because capital controls and credit risk premiums distorted forward pricing.
Case B: Switzerland (open, stable)
Swiss franc typically trades above PPP value due to safe-haven flows.
CIRP holds nearly perfectly; PPP consistently underpredicts CHF strength.
Case C: Argentina (closed/restricted)
Exchange rate multiple (official vs black market).
PPP is meaningless with two parallel rates.
IRP does not apply because access to FX derivatives is limited and arbitrage is not possible.
5. Lessons from Comparison
Open Developed Markets: CIRP nearly perfect; PPP valid in long run.
Emerging Markets: CIRP holds in interbank space, PPP holds weakly; capital flows and risk premia dominate.
Closed Economies: Both theories often fail; policy and controls override parity.
6. India’s Transition: From Closed to Semi-Open
Pre-1991: Neither PPP nor IRP operationally held; FX rate was administered.
1991–2000: Liberalisation opened markets gradually; PPP began to show weak long-run relevance, but CIRP was not accessible for corporates due to regulation.
2000 onwards: Increasing integration; today, CIRP is meaningful in interbank markets, and PPP works only as long-run anchor.
Still not fully open: Residual capital controls, RBI intervention, and shallow derivative markets mean both theories only partially hold.
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