Direct Answer
The PX Index is a rule-based measurement of major Czech equity benchmark, maintained by Prague Stock Exchange. 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 PX Index covers major Czech equity benchmark, within the Czech Republic market. Prague Stock Exchange 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
Weighted by free float market capitalization: shares times price times a free float factor, which rounds up in steps of 0.10, times a reduction factor. The free float adjusted weight of one issuer may not exceed 20% on the quarterly cut off dates, and the reduction factor, which can fall as low as 0.01, enforces this. It is a price index that ignores dividends.
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
Blue chip shares from the Prime and Standard markets, with Start and Free Market shares judged separately by the Index Committee. A share needs market capitalization above CZK 0.5 billion or average daily volume above CZK 2 million, and must have traded in at least 90% of sessions in the six month period. Investment fund shares, preference shares (in general) and equity derivatives are ineligible.
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
At the cut off date an issue must have been traded in at least 10 sessions, including conditional trading. If it has traded for under six calendar months but more than 10 days, the 90% trading ratio is counted from the start of trading.
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 Index Committee meets on the first trading day after the last session of February, May, August and November. The updated composition and calculation factors take effect on the first session after the third Friday of March, June, September and December.
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
Free float is defined by low thresholds: holdings above 5% by companies, governments, employees or insiders are excluded, but investment and mutual funds only count as strategic above 25%. A constituent that misses the inclusion criteria on two consecutive cut off dates is removed.
References
- Prague Stock Exchange: Prague Stock Exchange, Rules for the PX, PX TR and PX TRnet Indices, version 2.3 of June 2020, as published 2020. Every rule described on this page is taken from this document.
Current PX Index constituents
Prague Stock Exchange publishes and licenses the PX 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.
- Europe 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 PX Index?
Prague Stock Exchange maintains the PX Index and publishes the methodology document that defines its eligibility and weighting rules.
What does the PX Index measure?
It measures major Czech 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 PX Index constituents?
Prague Stock Exchange publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.