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Statistical composite that measures changes in the economy or in financial markets, often expressed in percentage changes from a base year or from the previous month. Indexes measure the ups and downs of stock, bond, and some commodities markets, in terms of market prices and weighting of companies in the index.


A statistical measure of the value of a certain portfolio of securities. The portfolio may be for a certain class of security, a certain industry, or may include the most important securities in a given market, among other options. The value of an index increases when the aggregate value of the underlying securities increases, and decreases when the aggregate value decreases. An index may track stocks, bonds, mutual funds, and any other security or investment vehicle, including other indices. An index's value may be weighted; for example, securities with higher prices or greater market capitalization may affect the index's value more than others. One of the most prominent examples of an index is the Dow Jones Industrial Average, which is weighted for price and tracks 30 stocks important in American markets.


The relative value of a variable in comparison with itself on a different date. Many security price indicators such as the Standard & Poor's series and the New York Stock Exchange series are constructed as indexes. Also called stock index. See also base period.


To adjust a variable by a selected measure of relative value. For example, it has been proposed that an investor's basis on a security be indexed for changes in consumer prices so that only real increases in value will be taxed. Also called tax indexing. See also subindex.


An index reports changes up or down, usually expressed as points and as a percentage, in a specific financial market, in a number of related markets, or in an economy as a whole.

Each index -- and there are a large number of them -- measures the market or economy it tracks from a specific starting point. That point might be as recent as the previous day or many years in the past.

For those reasons, indexes are often used as performance benchmarks against which to measure the return of investments that resemble those tracked by the index.

A market index may be calculated arithmetically or geometrically. That's one reason two indexes tracking similar markets may report different results. Further, some indexes are weighted and others are not.

Weighting means giving more significance to some elements in the index than to others. For example, a market capitalization weighted index is more influenced by price changes in the stock of its largest companies than by price changes in the stock of its smaller companies.


(1) A statistical indicator that measures changes in the economy in general or in particular areas.An example is the cost-of-living index.(2) A reference point against which measurements are taken for purposes of making future adjustments.An adjustable-rate mortgage might begin with an interest rate of 6 percent and provide that it will increase or decrease in a like percentage as the increase or decrease between today's quoted price for 10-year U.S.Treasury bonds and the price on the loan's annual anniversary date.We would say that 10-year T-bonds are the index.

Some leading loan indices include

• Wall Street Journal prime
• Federal discount rate
• Fed funds rate
• 11th District Cost of Funds
• 10-year Treasuries
• One-year LIBOR

References in periodicals archive ?
Moderate-quality evidence showed that mandibular advancement devices improve scores on the apnea-hypopnea index and the arousal index.
There was no significant difference between the young and middle-aged OSA groups in apnea-hypopnea index.
2 percent of patients with mild OSA, which was defined as an apnea-hypopnea index (AHI) of five to less than 15 breathing pauses per hour of sleep.
Patients were defined as having moderate to severe OSA if they had more than 20 apneas and hypopneas per hour of sleep (their apnea-hypopnea index was greater than 20).
Seven patients were diagnosed with OSAS, and their mean apnea-hypopnea index (AHI) was 19.
The current standard of care for sleep apnea patients is treatment of the disease using a variation of a continuous positive airway pressure device (CPAP), which has been shown to be effective in reducing the apnea-hypopnea index in sleep apnea patients.
In univariate analyses, the mean apnea-hypopnea index, ODI, and nighttime cortisol levels were significantly associated with global deficit scores and particularly with domains of learning, memory, and working memory, said the investigators.
By comparing the pre- and postoperative airway dimensions, skeletal changes, apnea-hypopnea index, and pressure effort of the 3-dimensional models, the researchers were able to interpret the surgical results.
Sleep-disordered breathing was defined as an apnea-hypopnea index (AHI) score of 5 or greater, representing the mean number of apnea and hypopnea events per hour of sleep.
The findings show the HGNS System reduced the severity of OSA by an average of over 50%, as measured by the apnea-hypopnea index (AHI).