Direct Answer
The TOPIX Small is a rule-based measurement of Japanese small-cap 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 TOPIX Small covers Japanese small-cap 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 index name does not state a fixed company count, so the number of constituents follows the eligibility rules rather than a target.
How constituents are weighted
Free float adjusted market capitalization weighted, using the same free float weight that TOPIX uses and the market cap weighting formula in the Index Calculation Guidebook. Price return and total return versions are calculated.
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
Every issue selected in the TOPIX periodic review except the constituents of TOPIX 500. It is a residual group, so it includes the TOPIX Small500 constituents and the issues in TOPIX Micro Cap.
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.
When the membership is revised
Reviewed annually in October with a base date of the last business day of August, results published on the fifth business day of October and applied from the last business day of October. Between reviews, a newly listed issue lands in Small (as Small500 or Micro Cap) when it misses the top 400 by market cap and top 1,000 by trading value needed for Mid400, and delistings are not backfilled until the next 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
TOPIX Small has no fixed count of constituents because it is defined by exclusion rather than by a ranking cutoff. It holds everything in TOPIX outside the 500 largest by the TOPIX 500 selection rules.
References
- JPX/Nikkei: JPX Market Innovation and Research TSE Index Guidebook (TOPIX New Index Series, Size based TOPIX Sub Indices), November 2, 2026 edition published July 24, 2026, as published 2026. Every rule described on this page is taken from this document.
Current TOPIX Small constituents
JPX/Nikkei publishes and licenses the TOPIX Small constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.
Related reading
- All stock market indexes: how indexes are built, weighted and revised.
- Asia-Pacific indexes: others covering the same region.
- Index concentration: measuring how much of an index sits in its largest holdings.
- Index rebalancing and inclusion effects: what happens to a stock when index membership changes.
Frequently Asked Questions
Who maintains the TOPIX Small?
JPX/Nikkei maintains the TOPIX Small and publishes the methodology document that defines its eligibility and weighting rules.
What does the TOPIX Small measure?
It measures Japanese small-cap 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 TOPIX Small 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.