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Law of One Price


The Law of One Price is an economic principle stating that identical goods or assets should sell for the same price in different markets when there are no transportation costs and no differential taxes applied in the two markets. It assumes no transaction costs, perfect information, and the absence of price discrimination. The concept is often used to explain exchange rate and purchasing power parity theories.


The phonetics for “Law of One Price” are:L – æ – w ə – v w – ʌ – n p – r – aɪ – s

Key Takeaways

  1. Law of One Price proposes that identical goods or services should have the same price across different markets when transportation and transaction costs are not considered.
  2. This principle becomes the basis for the theory of purchasing power parity (PPP) and is used in the analysis of exchange rates, international trade, and global economic policies.
  3. However, in the real world, there are various factors like taxes, tariffs, consumer preferences, and differences in market structures that can cause the Law of One Price to not hold true across different markets.


The Law of One Price is an important concept in business and finance as it states that identical goods should sell for the same price in different markets, assuming no transportation costs or other frictions. This principle underpins the idea of market efficiency and arbitrage, whereby differences in prices across markets provide opportunities for buyers or sellers to profit from such discrepancies until the equilibrium is restored. By adhering to this law, it ensures fair competition, promotes transparency, and helps maintain a robust market system, ultimately benefiting consumers and businesses alike through accurate price discovery, efficient allocation of resources, and reduced chances of market manipulation or distortion.


The Law of One Price serves as a fundamental concept in economics and finance, playing a crucial role in the understanding of price levels, exchange rates, and purchasing power. The principle hinges on the idea that identical goods should have the same price across different markets when expressed in a common currency. In essence, the Law of One Price aims to eliminate opportunities for arbitrage – the practice of taking advantage of price differences for the same item across separate markets. By doing so, the law strives to ensure market efficiency and encourage healthy competition, ultimately fostering the proper allocation of resources and promoting stable economic environments. In practice, the Law of One Price is an essential component of international trade and finance. It serves as the basis for calculating exchange rates and determining the purchasing power parity between different currencies, allowing for more accurate price comparisons of goods and services across countries. By enabling market participants to gauge the relative costs of goods and services, the Law of One Price also facilitates better decision-making regarding product sourcing, import/export strategies, and investment opportunities. Although the law may not always hold true in reality due to factors such as transportation costs, taxes, and market frictions, it remains a vital theoretical concept that allows economists and financial professionals to evaluate prices, examine exchange rate movements, and assess overall market efficiency.


The Law of One Price (LOOP) states that identical goods should sell for the same price in two separate markets when there are no transportation costs and no differential taxes applied in the two markets. Here are three real-world examples illustrating the concept of the Law of One Price: 1. Exchange Rates and Purchasing Power Parity (PPP): The LOOP plays a significant role in the determination of exchange rates by purchasing power parity theory, which suggests that identical goods in two countries should cost the same when expressed in a common currency. For example, if the price of a MacBook is 1200 USD in the United States and 1080 EUR in Europe, the implied exchange rate should be 1 USD = 0.9 EUR to maintain parity by eliminating any potential arbitrage opportunities. 2. Cross-Border Retail Arbitrage: The European Union’s single market exemplifies the Law of One Price in the retail sector. As a single market, the EU eliminates trade barriers, taxes, and transportation costs, allowing consumers to buy goods from other European countries without facing significant differences in price. For instance, if a French wine costs 10 EUR in France and the same wine is sold for 13 EUR in Germany, a consumer from Germany may choose to buy the wine directly from France, leading prices to eventually equalize between the countries. 3. Commodity Markets: Global commodity markets, like crude oil, also demonstrate the Law of One Price. Due to highly efficient trading systems and relatively low transportation costs, the price of identical commodities converges across different markets. For example, if there is a significant price difference for a barrel of oil in the United States and the United Kingdom, traders could profit from arbitrage opportunities by buying the cheaper oil and selling it where it’s priced higher until the LOOP is restored.

Frequently Asked Questions(FAQ)

What is the Law of One Price?
The Law of One Price is an economic principle stating that identical goods or assets should have a single price when accounting for exchange rates, transportation costs, and taxes. This concept assumes that markets are efficient, and there are no transportation or transaction costs, which leads to uniform pricing.
Is the Law of One Price always applicable in real life?
While the Law of One Price provides a theoretical benchmark, it may not perfectly hold in real life due to multiple factors, including transportation costs, market inefficiencies, taxes, tariffs, and differences in demand across regions.
What is the connection between the Law of One Price and purchasing power parity (PPP)?
Purchasing Power Parity (PPP) is an economic theory that expands on the Law of One Price. It states that the exchange rate between two currencies should be equal to the ratio of price levels of goods and services in those two countries. In essence, PPP is an application of the Law of One Price across countries, considering a basket of goods rather than a single product.
How does the Law of One Price affect international trade?
The Law of One Price plays a crucial role in international trade by promoting price equalization across countries. If there is a significant price difference of identical goods between countries, consumers will turn to the cheaper options. This incentivizes traders to buy low and sell high, leading to an increase or decrease in demand, eventually equalizing the prices.
Can the Law of One Price be used to detect arbitrage opportunities?
Yes, the Law of One Price can be used as a basis to identify potential arbitrage opportunities. If a good or asset has different prices in separate markets, an investor can profit by simultaneously buying low in one market and selling high in another market. However, these opportunities tend to be short-lived as traders exploit the price differences, leading to price equalization.
What factors can hinder the Law of One Price from holding true?
Several factors might prevent the Law of One Price from holding true in real life. These include:1. Transportation costs: Moving goods between markets involves costs, which can contribute to price discrepancies.2. Taxes and tariffs: Different countries impose different taxes and tariffs on goods, leading to variations in final prices.3. Market inefficiencies: Lack of perfect information and differing market conditions can cause price discrepancies.4. Non-traded costs: Local costs for providing certain goods or services, like labor and rent, can result in price disparities.5. Product differentiation: Even when goods appear identical, slight variations or branding can lead to different prices.
Why is the Law of One Price important for financial markets?
The Law of One Price is crucial for financial markets as it ensures efficiency and fairness in pricing of assets like stocks, bonds, and commodities. The efficient market hypothesis relies on the Law of One Price, which posits that, barring market imperfections, identical assets should have similar prices. This helps investors accurately evaluate investments and make informed decisions.

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