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'''[[SPDR index]]''' is a financial market index designed to measure the performance of a group of securities tracked by one or more [[SPDR exchange-traded fund|SPDR exchange-traded funds]] (ETFs). SPDR indices serve as benchmarks for investment products that seek to replicate the performance of specified market segments, sectors, asset classes, or investment strategies. They are generally constructed using transparent, rules-based methodologies that define constituent eligibility, weighting, index calculation, [[Corporate action adjustment|corporate action adjustments]], [[Index rebalancing|rebalancing]], and [[Index reconstitution|reconstitution]] procedures.

The term ''SPDR'' originally referred to '''Standard & Poor's Depositary Receipts''', the exchange-traded fund introduced in 1993 to track the [[S&P 500]]. Over time, the SPDR brand expanded to encompass numerous exchange-traded funds covering domestic and international equities, fixed income, commodities, and sector-specific investments. These funds generally seek to replicate the performance of an underlying index rather than outperform it through active security selection.

SPDR indices commonly employ [[Float-adjusted shares|float-adjusted market capitalization]] weighting, although alternative weighting methodologies such as equal weighting, factor weighting, and thematic weighting may also be used depending on the investment objective. Their methodologies are designed to ensure transparency, investability, and consistency while facilitating passive investment strategies.

SPDR indices are widely used by institutional investors, asset managers, pension funds, financial advisers, and individual investors for investment benchmarking, portfolio construction, passive investing, and performance measurement.

== History ==
The first SPDR exchange-traded fund was launched in 1993 to track the [[S&P 500]], becoming one of the world's first and largest exchange-traded funds.

As the ETF industry expanded, the SPDR product family introduced numerous funds tracking broad market, sector, international, and fixed-income indices. Corresponding benchmark indices evolved to support the growing range of passive investment products and diversified investment strategies.

Today, SPDR-branded investment products represent one of the largest families of exchange-traded funds globally.

== Objectives ==
The principal objectives of SPDR indices are to:

* measure market performance;
* support passive investing;
* provide transparent investment benchmarks;
* facilitate portfolio diversification;
* improve investment comparability;
* enable index-based investment products.

These objectives contribute to efficient and rules-based investment management.

== Construction methodology ==
A typical SPDR index methodology specifies:

* constituent eligibility;
* security selection;
* weighting methodology;
* index calculation;
* [[Corporate action adjustment|corporate action adjustments]];
* [[Index rebalancing|rebalancing]];
* [[Index reconstitution|reconstitution]].

These rules are intended to ensure that the index remains transparent, representative, and investable.

== Weighting methodology ==
Many SPDR indices employ:

* [[Float-adjusted shares|float-adjusted market capitalization weighting]];
* equal weighting;
* factor weighting;
* thematic weighting.

The weighting methodology depends on the objective of the underlying investment strategy.

== Example ==
Suppose a SPDR index tracks the largest publicly traded companies in a particular market.

If '''ABC Corporation''' has a float-adjusted market capitalization of '''US$500 billion''' and represents '''5%''' of the total float-adjusted market capitalization of all constituent companies, its index weight is approximately '''5%'''.

If the company's market capitalization increases relative to other constituents, its weight generally increases until the next scheduled [[Index rebalancing|rebalancing]] or other index maintenance event.

== Relationship with exchange-traded funds ==
SPDR indices serve as benchmarks for many [[Exchange-traded fund|exchange-traded funds]].

Index-tracking funds seek to replicate the performance of the underlying index by holding constituent securities in approximately the same proportions specified by the index methodology.

== Relationship with passive investing ==
SPDR indices are widely used in [[Passive investing]].

Rather than selecting securities through active management, passive investment funds seek to match the performance of the underlying benchmark index as closely as possible.

== Relationship with index mathematics methodology ==
[[Index mathematics methodology]] specifies the mathematical procedures used to calculate SPDR indices.

These procedures include:

* index calculation formulas;
* [[Index divisor]] adjustments;
* return calculations;
* treatment of corporate actions.

== Relationship with corporate action adjustment ==
[[Corporate action adjustment]] ensures that stock splits, rights offerings, mergers, spin-offs, and other structural corporate events do not create artificial changes in index values.

Such adjustments preserve the continuity and comparability of the index.

== Relationship with index rebalancing ==
[[Index rebalancing]] periodically adjusts constituent weights to maintain consistency with the published weighting methodology.

Rebalancing helps ensure that the index continues to reflect its intended market exposure.

== Relationship with index reconstitution ==
[[Index reconstitution]] periodically reviews constituent eligibility and adds or removes securities according to the published methodology.

Reconstitution ensures that the index remains representative of its target investment universe.

== Applications ==
SPDR indices are widely used in:

* exchange-traded funds;
* portfolio benchmarking;
* institutional asset management;
* passive investment strategies;
* performance measurement;
* financial research.

They also support the development of index-linked investment products.

== Advantages ==
SPDR indices provide several important benefits.

They offer transparent methodologies, broad market exposure, low-cost investment benchmarking, diversification, efficient portfolio construction, and objective performance measurement.

Their rules-based approach promotes consistency and replicability.

== Limitations ==
SPDR indices are subject to the limitations of index investing. They do not seek to outperform the market and remain exposed to market risk, sector concentration, and the assumptions embedded within their published methodologies.

Changes in market structure or index methodology may also affect index composition and investment performance.

== Importance ==
SPDR indices are among the most widely followed benchmarks supporting exchange-traded funds and passive investment strategies. By providing transparent, rules-based measures of market performance, they facilitate efficient portfolio management, investment benchmarking, and long-term capital allocation across global financial markets.

== See also ==

* [[Exchange-traded fund]]
* [[Passive investing]]
* [[S&P 500]]
* [[Index construction methodology]]
* [[Index mathematics methodology]]
* [[Index rebalancing]]
* [[Index reconstitution]]
* [[Float-adjusted shares]]
* [[Market capitalization-weighted index]]
* [[Index divisor]]