Nikkei 225
Nikkei 225, formally known as the Nikkei Stock Average (Nikkei Heikin Kabuka, 日経平均株価), is a stock market index that measures the performance of 225 leading companies listed on the Tokyo Stock Exchange (TSE). First published on 7 September 1950, the index is one of the principal indicators of the Japanese equity market and is widely regarded as a benchmark for the country's economy and corporate sector. The Nikkei 225 is a price-weighted index, meaning that its constituent companies are weighted according to their share prices rather than their market capitalization. The index is calculated and published by Nikkei, Inc., a Japanese media company, and includes companies from a broad range of industries, including manufacturing, technology, finance, pharmaceuticals, consumer goods, transportation, and telecommunications.
History
The origins of the Nikkei 225 date to the post-Second World War reconstruction of Japan's financial markets. The index was retrospectively calculated from 16 May 1949 and officially began publication on 7 September 1950 under the name Nikkei Dow Jones Average, reflecting its methodological similarities to the Dow Jones Industrial Average.
Initially developed in cooperation with Dow Jones & Company, the index was renamed the Nikkei Stock Average in 1975 after the licensing agreement with Dow Jones concluded. Since then, it has become the most widely followed indicator of Japan's stock market performance.
The index experienced rapid growth during Japan's asset price boom of the 1980s, reaching an all-time high of 38,915.87 points on 29 December 1989 during the Japanese asset price bubble. Following the collapse of the bubble, the index declined significantly and remained below its 1989 peak for several decades before surpassing that level in 2024.
Methodology
The Nikkei 225 is a price-weighted index, in which constituent companies are weighted according to their individual share prices rather than their total market value.
Under this methodology:
- companies with higher share prices exert greater influence on the index;
- company size is not directly reflected in constituent weight;
- stock splits and corporate actions require adjustments to the index divisor.
The methodology differs from most major global equity indices, including the S&P 500, NASDAQ Composite, and TOPIX, which employ market capitalization weighting.
Composition
The Nikkei 225 consists of 225 selected companies listed on the Prime Market of the Tokyo Stock Exchange.
Constituent companies are selected to represent a broad cross-section of the Japanese economy, including sectors such as:
- technology
- electronics
- automobiles
- industrial machinery
- chemicals
- pharmaceuticals
- banking
- insurance
- retail
- telecommunications
- transportation
- consumer goods
The composition of the index is reviewed periodically by Nikkei, Inc. to reflect changes in the Japanese economy and equity market.
Calculation
The Nikkei 225 is calculated by summing the adjusted share prices of all constituent companies and dividing the result by an index divisor.
The divisor is periodically adjusted to maintain continuity following corporate actions such as:
- stock splits
- share consolidations
- constituent replacements
- mergers
- corporate restructurings
These adjustments ensure that changes unrelated to market performance do not artificially affect the index level.
Selection criteria
Constituent companies are selected by Nikkei, Inc. according to criteria that include:
- liquidity
- trading activity
- sector representation
- market importance
- continuity of index composition
Periodic reviews may result in additions or removals of constituent companies in order to maintain the representativeness of the index.
Relationship with TOPIX
The Nikkei 225 is often compared with the Tokyo Stock Price Index (TOPIX), another major Japanese stock market index.
Key differences include:
| Characteristic | Nikkei 225 | TOPIX |
|---|---|---|
| Number of constituents | 225 | Broad market index |
| Weighting method | Price-weighted | Free-float market capitalization-weighted |
| Index provider | Nikkei, Inc. | Japan Exchange Group |
| Primary purpose | Benchmark of leading Japanese companies | Broad representation of the Tokyo Stock Exchange |
Because of its price-weighted methodology, the Nikkei 225 may be more heavily influenced by companies with relatively high share prices, whereas TOPIX reflects the aggregate market value of listed companies.
Applications
The Nikkei 225 serves as a benchmark for investors, asset managers, economists, and policymakers.
Its principal applications include:
- measuring Japanese equity market performance
- benchmarking investment portfolios
- supporting index funds
- supporting exchange-traded funds
- futures trading
- options trading
- economic analysis
- financial research
Numerous financial products, including derivatives and exchange-traded funds, track the performance of the index.
Impact
The Nikkei 225 is one of the world's most widely recognized stock market indices and serves as a leading indicator of investor sentiment toward the Japanese economy. Its movements reflect developments in Japan's corporate sector, monetary policy, international trade, exchange rates, and global financial markets. As Japan remains one of the world's largest economies, the performance of the Nikkei 225 is closely monitored by investors and policymakers worldwide. The index has also become a widely used benchmark for international investment in Japanese equities.