Direct Answer
The AMX (AEX Mid-Cap Index) covers 25 mid-cap Dutch companies listed on Euronext Amsterdam that rank immediately below the AEX 25 in free-float-adjusted market capitalisation. Administered by Euronext, it uses free-float-adjusted market-cap weighting and serves as the primary mid-cap benchmark for the Dutch equity market.
What this index covers
The AMX (AEX Mid-Cap Index) covers the Netherlands equity market through the Euronext Amsterdam. Euronext defines which securities are eligible, how they are selected from that pool and how much each contributes to the published number.
The eligible universe is: The 25 Euronext Amsterdam listed companies ranked 26 to 50 by free-float-adjusted market capitalisation among those eligible for the AEX index family, per the Euronext published methodology.
Understanding the eligible universe is the most important step in understanding what an index measures. An index that selects by listing venue will behave differently from one that selects by company domicile, and a sector index will have very different risk characteristics from a broad market measure even if they share some constituents.
How constituents are weighted
Free-float-adjusted market-capitalisation weighting. A single-stock weight cap may apply, per the published Euronext methodology.
Weighting is the mechanism that translates a list of companies into a single number. Free-float-adjusted market-capitalisation weighting is the most common method: larger companies contribute more to the index level than smaller ones, and the free-float adjustment excludes shares that are not available to public investors (such as government-held strategic stakes or closely-held founder shares). This makes the index level reflect the actual investable market rather than total market size.
Eligible universe and eligibility rules
Eligibility rules determine which companies can be included at a review and which must exit. The key dimensions to verify are: which exchange or market segment is in scope; whether domicile or listing venue determines eligibility; the minimum free-float threshold; the liquidity screen; and whether there are sector restrictions.
For the AMX (AEX Mid-Cap Index), the relevant market is the Euronext Amsterdam and the administrator is Euronext. Per the published Euronext methodology (verification date: August 31, 2026), the eligible universe is defined as: The 25 Euronext Amsterdam listed companies ranked 26 to 50 by free-float-adjusted market capitalisation among those eligible for the AEX index family, per the Euronext published methodology.
Reconstitution schedule
Quarterly, aligned with the AEX review schedule. Promotion into the AEX or relegation to the ASCX can occur at each review.
Reconstitution is the date on which the index changes shape by design rather than by price. Passive funds tracking the index must trade toward the new membership list, which creates predictable order flow around the review date. Active managers often position around reconstitution events to capture or avoid that flow.
How investors use this index
Dutch mid-cap benchmark; provides targeted exposure to the segment between Dutch large-cap blue chips and small-caps; used by funds seeking mid-market Netherlands exposure and for index inclusion event strategies.
For any index, three uses are distinct: as a performance benchmark (measuring how well a portfolio did relative to the market), as a product underlying (an ETF or structured product replicating the index), and as a research reference (tracking market-cap, sector weights or concentration over time). The same index can serve all three purposes, but the choice of which to use depends on the investment mandate and the specific question being answered.
Comparisons with related indexes
The AMX (AEX Mid-Cap Index) is most often compared with:
- AEX: the 25 largest Dutch blue chips; AMX covers the next 25 companies by float-adj market cap.
- ASCX: Dutch small-cap index; the AMX is one size tier above the ASCX.
- AEX All-Share: covers all qualifying Dutch listings including large, mid and small; AMX is the mid-cap slice.
When switching from one benchmark to another, the practical question is what changes in coverage: does the alternative add smaller companies, exclude a sector, change the weighting method or extend to a different currency? Each of these changes alters what the index can tell you about market performance.
References
- Euronext: Index Products, as published per the provider's methodology page. All methodology claims on this page are derived from this source.
Current AMX (AEX Mid-Cap Index) constituents
Euronext publishes and licenses the AMX (AEX Mid-Cap Index) 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.
- European Stock Market 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 administers the AMX?
Euronext administers the AMX under its published index methodology.
What does AMX stand for?
AMX stands for AEX Mid-Cap Index. It is sometimes referred to simply as the AEX Mid-Cap.
How does the AMX relate to the AEX?
The AEX selects the 25 largest qualifying Dutch companies. The AMX covers the next 25 by float-adjusted market capitalisation, ranked approximately 26 to 50 within the eligible Dutch universe.
How often is the AMX reconstituted?
Quarterly, on the same schedule as the AEX. At each review, the largest AMX companies may be promoted to the AEX and the smallest may be relegated to the ASCX.
Where can I find current AMX data?
Euronext publishes AMX constituent and level data on its official index pages. Swoopr does not republish licensed constituent lists.