Answer:
Market performance in the United States is tracked using stock indexes, which use formulas to calculate price changes.
Step-by-step explanation:
A stock market index is a measurement of a section of the stock market. This is a tool that is used by investors and financial managers in order to track market performance. A stock market index can help us describe the market and compare the return of various investments. An example of a stock market index is the New York Stock Exchange located on Wall Street.