Purchasing Power ParityPPP
Purchasing power parity is the idea that exchange rates should, over the long run, move towards the rate that makes the same basket of goods cost the same in both countries. Currencies can stay far from PPP for years, so it is a valuation guide, not a timing tool.
Purchasing power parity asks what exchange rate would make the same goods cost the same in two countries. Comparing that rate with the market rate gives a rough sense of whether a currency looks cheap or expensive, though currencies can sit far from PPP for years.
- Category
- Fundamentals and Macroeconomics
- Reading time
- 4 min
- Also called
- PPP exchange rate, Law of one price (aggregate), PPP theory
- Updated
PPP in plain words
PPP is the exchange rate at which the same basket of goods and services would cost the same in both countries.1
A classic example: if a hamburger costs £2 in London and $4 in New York, the implied PPP rate is £1 = $2.1
Official PPP figures come from big international price surveys run by the World Bank's International Comparison Program.2
How to use PPP as a currency guide
Pick a basket
Compare prices of the same goods in two countries.
Compute the implied rate
Divide one price by the other — as in the hamburger example, which gives £1 = $2.1
Compare with the market rate
If the market rate differs, the currency looks over- or undervalued against PPP.
Use official data
Prefer survey-based PPPs from the International Comparison Program.2
Allow for estimation error
Remember PPP figures between surveys are estimates, so they can be off.1
Think long term
Treat gaps as slow valuation signals: PPP rates move far less than market rates.1
Worked examples
Example 1 — Implied rate
PPP rateA hypothetical basket costs €100 in the euro area and $120 in the US.
| Euro price | €100 |
| Dollar price | $120 |
| Implied PPP | €1 = $1.20 |
That is the rate at which the same goods would cost the same in both countries.1
Example 2 — Undervalued?
Valuation, not timingThe hypothetical market rate is €1 = $1.05 while PPP is €1 = $1.20.
| Market rate | $1.05 |
| Gap vs PPP | −12.5% |
The euro looks cheap on PPP, but PPP moves slowly compared with markets, so the gap can last a long time.1
Example 3 — Emerging market
Normal gapA hypothetical emerging currency trades at 3× its PPP rate against the dollar.
| Market ÷ PPP | 3 |
Big gaps are normal: in many emerging economies, the market rate is two to four times the PPP rate.1
PPP rate vs market exchange rate
| Aspect | PPP rate | Market rate |
|---|---|---|
| Based on | Relative prices of goods | Supply and demand for currency |
| Volatility | Low | High |
| Main use | Comparing living standards | Trading and payments |
| Data frequency | Infrequent surveys | Continuous |
Where PPP is used
Currency valuation
A long-run anchor for Mean Reversion views on exchange rates.
Comparing economies
Convert Gross Domestic Product at PPP to compare real output.
Inflation context
Price-level gaps link to Inflation differences.
Strategic allocation
Inform long-term currency Exposure decisions.
Advantages and disadvantages
Advantages
- Gives a fundamental anchor for exchange rates.
- More stable than market rates.
- Useful for comparing living standards.
- Backed by official international surveys.
Disadvantages
- Currencies can stay far from PPP for years.
- Non-traded goods distort comparisons.
- Surveys are infrequent and estimated in between.
- Useless as a short-term timing tool.
Going deeper
Read as far as you need. Each level builds on the one before it.
The basic idea
Beginner
PPP asks what exchange rate would make the same goods cost the same in both countries.1
How official PPPs are made
Intermediate
Why gaps persist
Advanced
In many emerging economies, market exchange rates sit two to four times away from PPP.1 Cheap non-traded services, capital flows and interest-rate differences keep market rates away from PPP, so it works as a valuation guide rather than a forecast.
Common mistakes
Using PPP to time trades
Gaps can last for years.
Expecting poor countries to converge
Large gaps are structural.
Relying on one product
Single-item indices are rough.
Ignoring estimation error
PPPs between surveys are estimates.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- PPP is the rate that equalises the cost of the same goods.
- Compare it with the market rate to judge valuation.
- PPP rates are stable; market rates are not.
- Big gaps are normal for emerging economies.
- Use it as a valuation guide, not a timing tool.
Frequently asked questions
Is the Big Mac index a PPP measure?
Why are poorer countries cheap at market rates?
Who publishes official PPPs?
Further learning
- Inflation
Price changes behind PPP shifts.
- Gross Domestic Product
Output comparisons at PPP.
- Mean Reversion
Why currencies may drift back.
- Interest Rate
What moves market exchange rates.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- International Monetary Fund (Finance & Development). Purchasing Power Parity: Weights Matter (opens in a new tab) Checked .
- World Bank. International Comparison Program (ICP) (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.