S&P/ASX MidCap 50: What It Measures and How It Is Built

Direct Answer

The S&P/ASX MidCap 50 is a rule-based measurement of mid-cap 50 companies ranked 51-100 by float-adjusted market cap on the ASX, maintained by S&P Dow Jones Indices/ASX. 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 S&P/ASX MidCap 50 covers mid-cap 50 companies ranked 51-100 by float-adjusted market cap on the ASX, within the Australia market. S&P Dow Jones Indices/ASX 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 50 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

Constituents are weighted by float-adjusted market capitalization (FMC) using the standard S&P Dow Jones divisor method. Share counts are reviewed quarterly and rounded to the nearest thousand.

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

Measures the MidCap component of the S&P/ASX 100, excluding the LargeCap component, so it is built from constituents of the S&P/ASX 100 hierarchy and carries the same GICS classification, float and liquidity requirements.

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

Market capitalization is measured on a six-month daily average. An IPO or direct listing is added only when a vacancy appears or at a rebalance, and only after proven liquidity for at least eight weeks, unless an extraordinary large offering justifies an exception.

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

The methodology states that it only rebalances when constituent changes are made in its respective underlying index, rather than on a calendar of its own.

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

The buffer table lists no rank buffers for it. Together with the S&P/ASX Small Ordinaries it makes up the S&P/ASX Mid-Small index, which is every S&P/ASX 300 company outside the S&P/ASX 50.

References

• S&P Dow Jones Indices/ASX: S&P Dow Jones Indices, S&P/ASX Australian Indices Methodology, as published 2025. Every rule described on this page is taken from this document.

Current S&P/ASX MidCap 50 constituents

S&P Dow Jones Indices/ASX publishes and licenses the S&P/ASX MidCap 50 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.

S&P Dow Jones Indices/ASX: official S&P/ASX MidCap 50 page

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