A Stock Market Index is a measure of the overall value of stocks on a particular market. Some are price-weighted and give greater weight to the larger companies, while others use proprietary methods to assign weightings. The most commonly followed indexes are the S&P 500, Dow Jones Industrial Average, and Nasdaq Composite. All of these indexes track the performance of many different stocks. To understand how they work, it helps to understand the structure of a stock market index.
A price-weighted index is calculated by adding the current share prices of all the companies in an index, and dividing this total by the number of the companies. However, the index calculation would remain simple if no changes in the share prices of component companies occurred. Changing prices of component companies can affect the index, so the index divisor is adjusted accordingly. This makes it easy to understand why the price of a stock can change by as much as 20%.
A Stock Market Index can help investors choose the best stocks to invest in. Without an index, the stock market is a chaotic place containing many different stocks. It’s hard to know which stocks are the best investments based on fundamentals or market sentiment. By providing investors with a reliable and efficient stock picking guide, stock market indices are beneficial to all types of investors. They are used as benchmarks to develop exchange-traded funds, index tracking funds, and derivatives.
The total Stock Market Index is a widely-used benchmark that attempts to capture the performance of the entire market. As such, it can also serve as a gauge of the health of the economy. It is possible to use an index to identify trends within a specific sector, such as tech stocks. But beware that an index is not a substitute for research and analysis. For example, the Dow Jones Wilshire 5000 Index was not used until June 2, 2013.
Indicators are based on the market capitalization of the companies. The larger the company, the larger its weight is. The index is logically based on the total market share value of the companies on that market at the time it is created. Therefore, changing stock prices have a direct impact on the index’s value. This way, index investors are assured of a consistent picture of what’s happening with their investments. The stock market index is not a perfect measure of the health of the economy.
In addition to the S&P 500 index, there are specialized indices that monitor specific sectors of the stock market. The Morgan Stanley Biotech Index tracks 36 biotechnology companies. While the Wilshire US REIT Index tracks 80 U.S. real estate investment trusts. To learn about how a Stock Market Index works, take a look at the values of stocks over time. The S&P 500 Index represents approximately 80% of the total U.S. stock market, and therefore is a useful indicator of the direction of the overall market.