Direct Answer
The MSCI ACWI IMI is a rule-based measurement of large-, mid-, and small-cap equities across 23 developed and 24 emerging market countries, maintained by MSCI. 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 MSCI ACWI IMI covers large-, mid-, and small-cap equities across 23 developed and 24 emerging market countries, within the Global market. MSCI 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
Constituents are weighted by free float-adjusted market capitalization, scaled by the Foreign Inclusion Factor. The index is a composite of the Investable Market Index of each developed and emerging market, built from non-overlapping Large, Mid and Small Cap segments, so no company is counted twice.
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
A company must clear the Equity Universe Minimum Size Requirement, set where the developed universe reaches 99% cumulative free float-adjusted coverage, and a security needs float-adjusted size of at least half of that. A security also needs a Foreign Inclusion Factor of 0.15 or more and, for developed markets, 20% 12-month and 3-month ATVR with 90% frequency of trading, or 15% and 80% for emerging markets. Each market targets about 99% coverage.
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
A new issue must have started trading at least three months before a review. Large IPOs and large offerings by non-constituents are not bound by this and can be added outside a review, with significantly large IPOs included after the close of their tenth trading day.
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
Quarterly reviews in February, May, August and November; for a February review the equity universe is fixed at the end of November, liquidity data at the end of December and prices on a day in the last ten business days of January, with the other reviews following the same pattern. Changes from corporate events between reviews are generally made as they occur.
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
Small caps are defined as the IMI minus the Standard Index, and a non-constituent inside the small cap entry buffer (1.5 times the cutoff) joins only to the extent it replaces a current constituent that fell below the lower buffer. The remaining candidates still count toward the segment size but stay out of the index.
References
- MSCI: MSCI GIMI Methodology: Index Construction Objectives, Guiding Principles and Methodology for the MSCI Global Investable Market Indexes, as published 2026. Every rule described on this page is taken from this document.
Current MSCI ACWI IMI constituents
MSCI publishes and licenses the MSCI ACWI IMI 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.
- Global 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 MSCI ACWI IMI?
MSCI maintains the MSCI ACWI IMI and publishes the methodology document that defines its eligibility and weighting rules.
What does the MSCI ACWI IMI measure?
It measures large-, mid-, and small-cap equities across 23 developed and 24 emerging market countries. 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 MSCI ACWI IMI constituents?
MSCI publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.