--- title: "JPX-Nikkei Index 400: Methodology" description: "JPX-Nikkei Index 400 is maintained by JPX/Nikkei and covers Japanese high-quality company equity benchmark. How the index selects and weights its constituents." canonical: https://www.getswoopr.com/stocks/indexes/jpx-nikkei-400/ source: "Swoopr Investment: https://www.getswoopr.com" --- # JPX-Nikkei Index 400: What It Measures and How It Is Built ## Direct Answer > The JPX-Nikkei Index 400 is a rule-based measurement of Japanese high-quality company equity benchmark, maintained by JPX/Nikkei. Like every index it owns nothing: it is a number produced by applying a published weighting formula to a selected list of companies, revised on a schedule the provider sets. ## What this index covers The JPX-Nikkei Index 400 covers Japanese high-quality company equity benchmark, within the Japan market. JPX/Nikkei defines which securities are eligible, how they are selected from that pool, and how much each one contributes to the published number. The name states a target of 400 companies. A target is not a guarantee of the exact count on any given day: corporate actions, dual share classes and pending additions all move the real number around it. ## How constituents are weighted Free float adjusted market capitalization weighted. The free float weight is multiplied by a cap adjustment factor so that no constituent exceeds a 1.5% weight on the periodic selection base date. That factor is not changed until the following year's application date, although an extraordinary revision can follow a merger or a large change in weight. The weighting method is the single biggest driver of how an index behaves. Two indexes covering the same market can diverge for years purely because they weight differently, which is why comparing index levels without knowing the method tells you very little. ## What qualifies for inclusion Common stocks whose main market is the TSE Prime, Standard or Growth market. Issues with liabilities exceeding assets, operating or overall losses in every year of the three year window, going concern notes, internal control deficiencies, delisting designations, certain exchange disciplinary actions or a RepRisk Index of 75 or higher are removed. The 1,000 largest by market cap among the 1,200 with the highest three year trading value are then scored. Eligibility rules are the part of an index most readers never look at and the part that decides what it can possibly measure. A screen that excludes a whole sector, or admits only one listing venue, shapes the result far more than any day of trading does. ## How long a listing must exist first Issues listed for under three years on the base date are removed from the eligible pool, except a company that came through a technical listing and had been listed for three or more years before its delisting. A seasoning rule is why a large new listing does not appear in an index the week it starts trading. It is a deliberate lag, and it means an index can under-represent a fast-growing part of the market for months at a time. ## When the membership is revised Annual review with a base date of the last business day of June. The list of additions and removals is released on the fifth business day of August and the new constituents apply from the last business day of August. The base number is 400. Between reviews, issues removed by delisting or other events are not replaced, so the count can fall below 400 until the next August review. Reconstitution is the one date an index changes shape by design rather than by price. Funds tracking it have to trade toward the new membership, which is why the schedule matters to anyone holding the tracker rather than only to the provider. ## The rule that surprises people Governance and disclosure count in selection. Qualitative scores for a majority of independent directors, at least 30% female board members and executive officers, IFRS adoption and English language disclosure are added to a score built 40% on three year average ROE, 40% on three year cumulative operating profit and 20% on market cap. Qualitative points are set so that at most around 10 constituents differ from a purely quantitative ranking. ## References - [JPX/Nikkei: JPX Market Innovation and Research and Nikkei Inc. JPX Nikkei Index 400 Guidebook (August 3, 2026 edition)](https://www.jpx.co.jp/english/markets/indices/line-up/files/e_cal2_1_jpx400.pdf), as published 2026. Every rule described on this page is taken from this document. ## Current JPX-Nikkei Index 400 constituents JPX/Nikkei publishes and licenses the JPX-Nikkei Index 400 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights. [JPX/Nikkei: official JPX-Nikkei Index 400 page](https://www.jpx.co.jp/english/markets/indices/index.html) ## Related reading - [All stock market indexes](https://www.getswoopr.com/stocks/indexes/): how indexes are built, weighted and revised. - [Asia-Pacific indexes](https://www.getswoopr.com/stocks/indexes/asia-pacific/): others covering the same region. - [Index concentration](https://www.getswoopr.com/technical-analysis/market-concentration/index-concentration/): measuring how much of an index sits in its largest holdings. - [Index rebalancing and inclusion effects](https://www.getswoopr.com/stocks/corporate-actions-catalysts/index-rebalancing-and-inclusion-effects/): what happens to a stock when index membership changes. ## Frequently Asked Questions ### Who maintains the JPX-Nikkei Index 400? JPX/Nikkei maintains the JPX-Nikkei Index 400 and publishes the methodology document that defines its eligibility and weighting rules. ### What does the JPX-Nikkei Index 400 measure? It measures Japanese high-quality company equity benchmark. The index is a calculated number applying a weighting formula to a selected list of companies, and it holds nothing itself. ### Where can I see the current JPX-Nikkei Index 400 constituents? JPX/Nikkei publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence. ## About the author The [Swoopr Editorial Team](https://www.getswoopr.com/authors/swoopr-editorial-team/) writes Swoopr Investment's educational library, covering market structure, analysis methods and the mechanics behind the numbers investors read every day. Our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/) set out how this content is produced, reviewed and fixed when it is wrong.