A Capitalization-weighted Index: NASDAQ Composite Index

Computers became a lot more advanced during the 1950s and 1960s. By the early 1970s, people who worked on Wall Street started to experiment with computers to see if they could be used to improve stock trading.
 
At the time, there wasn’t a good way to get stock price information—or stock “quotes”—to all investors at the same time. This made buying and selling stocks inefficient and expensive. The National Association of Securities Dealers (NASD), an agency that oversees the buying and selling of stocks, decided that computers could be used to solve this problem.
 
The NASD created a brand-new stock exchange in 1971. This new stock exchange would allow investors to buy and sell stocks on computers that were connected to each other. They called this new stock market the National Association of Securities Dealers Automated Quotations, or NASDAQ.

The NASDAQ stock exchange offered many advantages over other stock exchanges. Since all of the buying and selling was done on computers there was no need to have a physical trading floor. Accurate prices could also be viewed by all investors at the same time.
 
The inventors of the NASDAQ stock exchange also created an index that tracked the price movements of all the companies that were listed on the exchange. They called this new index the NASDAQ Composite Index. Today, there are more than 3,200 businesses that make up the NASDAQ Composite Index.
 
Like the S&P 500, the NASDAQ Composite Index is a capitalization-weighted index. This means that larger companies have a bigger influence over the movement of the NASDAQ Composite Index than smaller companies.

- Brian Feroldi, Why Does The Stock Market Go Up?:

Everything You Should Have Been Taught About Investing In School, But Weren't, 2022