What is Purchasing Power Parity (PPP)
Purchasing Power Parity (PPP) is one of the most fundamental concepts for theoretically calculating the appropriate level of exchange rates. It derives from the idea based on the law of one price that the same goods and services should be purchasable at the same price in different countries.
Basic Principle of PPP
If a Big Mac costs 390 yen in Japan and $5.69 in the US, the PPP-based exchange rate would be 390 / 5.69 = 68.5 yen/dollar.
When the actual exchange rate deviates from the PPP level, that currency is judged to be "undervalued" or "overvalued."
Historical Background of PPP Theory
PPP theory traces back to the School of Salamanca in the 16th century, but the modern formulation was established by Swedish economist Gustav Cassel in 1918.
| Era | Development | Key Contributors |
|---|---|---|
| 16th Century | Law of one price concept | School of Salamanca |
| 1918 | PPP theory formulation | Gustav Cassel |
| 1970s | Empirical research development | Central banks, IMF |
| 1986- | Big Mac Index | The Economist |
Why PPP Matters
- Long-term equilibrium exchange rate: Long-term tendency for exchange rates to converge to PPP
- Currency over/undervaluation judgment: Reference indicator for investment decisions
- International comparison standard: Basis for comparing GDP and living standards across countries
- Relationship with inflation: Theoretical basis for long-term depreciation of high-inflation country currencies
Types of PPP and Calculation Methods
There are multiple types of PPP, used according to purpose.
Absolute Purchasing Power Parity
Calculates exchange rates by comparing prices of identical baskets of goods and services.
Formula:
PPP Rate = Country A price basket / Country B price basket
Example:
- Japanese consumer price basket: 100,000 yen
- Equivalent US basket: $1,000
- PPP Rate: 100,000 / 1,000 = 100 yen/dollar
Relative Purchasing Power Parity
The concept that exchange rate change equals the inflation differential between two countries.
Formula:
Exchange rate change ≈ Country A inflation rate - Country B inflation rate
Example:
- Turkey inflation rate: 60%
- Japan inflation rate: 3%
- Theoretical lira depreciation: ~57%
Big Mac Index
A PPP indicator based on Big Mac prices published by The Economist since 1986.
| Pros | Cons |
|---|---|
| Simple and easy to understand | Single product limits representativeness |
| Easy data access | Includes non-tradable goods (services) |
| Regular updates | Doesn't reflect wage levels by country |
OECD PPP Rates
The OECD publishes PPP rates based on comprehensive price surveys, calculating more precise PPP from surveys of over 3,000 items.
PPP Data Sources
Data sources for conducting PPP analysis.
Major Data Sources
| Data Source | Content | Update Frequency | URL |
|---|---|---|---|
| OECD | Comprehensive PPP rates | Annual | data.oecd.org |
| World Bank | ICP (International Comparison Program) | Every 3-5 years | worldbank.org |
| IMF | WEO database | Semi-annual | imf.org |
| The Economist | Big Mac Index | Semi-annual | economist.com |
Points for Data Utilization
- Compare multiple sources: Don't rely on a single PPP, check multiple indicators
- Time series changes: Check trends from past, not just current point
- Calculate deviation rate: Understand difference from actual exchange rate as percentage
2024 Undervalued Currency Ranking
Here's the PPP-based undervalued currency ranking as of April 2024. Deviation rate shows how far actual exchange rate is from PPP level (negative = undervalued).
Developed Market Currency Undervaluation Ranking
| Rank | Currency | PPP Rate (vs USD) | Actual Rate | Deviation |
|---|---|---|---|---|
| 1 | Japanese Yen (JPY) | ~95 yen | ~155 yen | -39% |
| 2 | Korean Won (KRW) | ~950 | ~1,350 | -30% |
| 3 | British Pound (GBP) | ~0.72 | ~0.80 | -10% |
| 4 | Canadian Dollar (CAD) | ~1.25 | ~1.37 | -9% |
| 5 | Euro (EUR) | ~0.82 | ~0.93 | -12% |
Emerging Market Currency Undervaluation Ranking
| Rank | Currency | Deviation | Main Factors |
|---|---|---|---|
| 1 | Turkish Lira (TRY) | -72% | High inflation, political risk |
| 2 | South African Rand (ZAR) | -58% | Power crisis, structural issues |
| 3 | Indonesian Rupiah (IDR) | -52% | Current account deficit, EM risk |
| 4 | Indian Rupee (INR) | -48% | Inflation, capital outflow |
| 5 | Mexican Peso (MXN) | -35% | Emerging market premium |
| 6 | Brazilian Real (BRL) | -32% | Fiscal concerns, political risk |
| 7 | Chinese Yuan (CNY) | -28% | Property crisis, capital controls |
Overvalued Currencies
For reference, currencies evaluated as overvalued on PPP basis.
| Currency | Deviation | Main Factors |
|---|---|---|
| Swiss Franc (CHF) | +42% | Safe haven premium |
| Norwegian Krone (NOK) | +18% | Resource nation, high income |
Currency to Watch: Japanese Yen
The most notable as of 2024 is the significantly undervalued state of the Japanese Yen.
The Japanese Yen is exceptionally 39% undervalued for a developed market currency, levels not seen since the 1970s. With BOJ monetary policy normalization, long-term correction toward yen strength is expected.
Analysis Methodology
Practical methods for conducting PPP-based undervaluation/overvaluation analysis.
Deviation Rate Calculation
Formula:
Deviation Rate = (PPP Rate - Actual Rate) / Actual Rate x 100%
Example (USD/JPY):
- PPP Rate: 95 yen/dollar
- Actual Rate: 155 yen/dollar
- Deviation Rate: (95 - 155) / 155 x 100% = -39%
Duration Analysis of Deviation
PPP deviations can persist for extended periods. Analyzing deviation duration helps evaluate correction probability.
| Duration | Interpretation | Trading Implication |
|---|---|---|
| Under 1 year | Temporary deviation | Wait and see |
| 1-3 years | Possible structural factors | Factor analysis |
| 3-5 years | Long-term deviation, correction pressure building | Monitor reversal signs |
| 5+ years | Extreme deviation, high reversal risk | Consider long-term positions |
Balassa-Samuelson Effect Consideration
The phenomenon of emerging market currencies being chronically undervalued versus PPP is explained by the Balassa-Samuelson effect.
- Theory: Non-tradable goods prices are lower in less productive countries
- Implication: EM currency undervaluation is "natural"
- Adjustment: Use "adjusted PPP" adjusted for income levels
Income-Adjusted PPP Deviation
Calculate income level-adjusted PPP deviation.
Formula:
Adjusted Deviation = Actual Deviation - Expected Deviation (estimated from income level)
| Currency | Simple Deviation | Expected Deviation | Adjusted Deviation |
|---|---|---|---|
| Japanese Yen | -39% | 0% | -39% (abnormally undervalued) |
| Turkish Lira | -72% | -40% | -32% (undervalued) |
| Mexican Peso | -35% | -30% | -5% (near fair value) |
Trading Applications
How to apply PPP analysis to FX trading.
Strategy 1: Mean Reversion Strategy
Strategy based on the premise that PPP deviations are corrected long-term.
Entry Conditions
- Deviation exceeds 2 standard deviations from historical average
- Deviation has persisted for 3+ years
- Signs of fundamental improvement
Position Example: Long Yen
- Rationale: Yen 39% undervalued, historic levels
- Entry: Gradually build yen long position
- Target: 30%+ return from correction toward PPP (95 yen)
- Timeframe: 2-5 year long-term investment
Strategy 2: Carry Trade Screening
Use PPP analysis to refine carry trade currency selection.
| Currency | Rate Differential | PPP Deviation | Overall Assessment |
|---|---|---|---|
| Mexican Peso | High | Somewhat undervalued | Attractive |
| Turkish Lira | Very high | Significantly undervalued | High risk (may continue falling despite undervaluation) |
| Swiss Franc | Low | Overvalued | Avoid (short candidate) |
Strategy 3: Pair Trade
Pair trade combining two currencies with different PPP deviations.
Pair Example: Long Yen vs Short Swiss Franc
- Yen: 39% undervalued
- Swiss Franc: 42% overvalued
- Theoretical return opportunity: 81% deviation correction potential
- Risk: High correlation as both are safe-haven currencies
PPP Trade Timeframe
PPP-based trades are inherently long-term strategies. Short-term can deviate significantly from PPP levels, requiring multi-year investment horizons.
PPP Analysis Limitations
PPP analysis has important limitations. Understanding these when utilizing is critical.
1. Lack of Short-Term Predictive Power
PPP indicates long-term equilibrium levels and is not suitable for predicting short-term currency movements.
- Deviations can widen for years
- Combination with other indicators needed for short-term trading
2. Measurement Difficulties
Accurate PPP calculation faces the following challenges:
- Price basket composition differences
- Quality difference adjustments
- Non-tradable goods treatment
- Data availability
3. Structural Change Response
Economic structural changes may alter the appropriate PPP level itself.
- Productivity changes
- Trade structure changes
- Capital flow liberalization
4. "Undervalued" Does Not Equal "Will Rise"
The most important caveat is that undervalued currencies don't necessarily appreciate.
- Turkish Lira has been undervalued for years but continues falling
- As long as fundamentals continue deteriorating, even undervalued currencies fall
- PPP corrects "eventually" but "when" is unknown
5. Combine with Other Analysis
Recommended to combine PPP analysis with the following rather than standalone.
| Analysis Method | Complementary Perspective |
|---|---|
| Interest rate differential analysis | Short-medium term direction |
| Current account analysis | Capital flow sustainability |
| Political risk analysis | Sudden movement risk |
| Technical analysis | Entry/exit timing |
PPP analysis is a powerful tool for understanding long-term equilibrium exchange rate levels. However, simple judgment of "undervalued = buy" is dangerous. Make investment decisions after conducting multi-faceted analysis including fundamental changes, interest rate differentials, and political risk. The exceptional undervaluation of developed market currencies like the Japanese Yen may provide interesting opportunities for long-term investors, but timing requires caution.
Additional Editorial Notes
When reading PPP Analysis: Finding Undervalued Currencies in 2026, the practical question is not whether the theme sounds attractive. In Trading Techniques, readers need to separate time horizon, tax treatment, liquidity, currency exposure, and downside tolerance. Topics connected with purchasing power parity, PPP, fundamental analysis, currency theory, undervalued currencies can look simple in headlines, but the result often depends on several moving assumptions. This review adds a clearer framework for readers returning to the page later.
Using Purchasing Power Parity to identify undervalued currencies for long-term investment. Still, a short description cannot cover the full decision process. The same yield can mean different things when currency conversion, account type, fees, and exit timing are included. A reader should first decide whether the money is short-term cash, medium-term savings, or long-term capital before drawing conclusions from market commentary.
How to Read This Page
| Lens | What to Check | Common Mistake |
|---|---|---|
| Time horizon | Separate near-term cash from long-term capital | Reacting to short-term moves with long-term money |
| Currency | Compare local-currency and home-currency outcomes | Treating currency gains as fundamental performance |
| Costs | Add fees, spreads, taxes, and fund expenses | Comparing only headline yields or returns |
| Liquidity | Check whether funds can be accessed when needed | Assuming normal-market conditions during stress |
PPP Analysis: Finding Undervalued Currencies in 2026 is most useful when treated as a decision framework, not a single answer. Before acting on any market view, define when the money will be used, what currency it will be spent in, and what condition would make the position too large.
- Cash buffer: keep essential spending separate from market exposure.
- Concentration: avoid stacking assets that all respond to the same factor.
- Review date: decide when rates, rules, fees, and risks will be checked again.
- Exit condition: write down what would justify reducing exposure.