Stock Market Indices

Introduction

An index is a number that tracks the performance of a group of stocks. It gives us a snapshot of how the market or a sector is doing without tracking every single stock. This lesson covers what indices are and how to read them.

What an Index Is

An index measures the average value of a chosen basket of stocks. When people say "the market went up," they usually mean an index went up.

Examples:

• S&P 500 — 500 large US companies
• Dow Jones Industrial Average — 30 large US companies
• NASDAQ Composite — many technology and growth companies
• FTSE 100 — 100 largest UK-listed companies

What Indices Are For

• Measuring performance — how is the market doing?
• Benchmarking — am I beating the market?
• Basis for products — index funds and ETFs track indices
• Sentiment — a quick read on investor mood

Index vs Single Stock

Single stock: one company's ups and downs
Index:        the average of many companies

An index smooths out the noise of individual stocks and reflects broader market trends.

Market Cap and Weighting

Most indices weight companies by market capitalization — bigger companies influence the index more. So the index moves with the largest, most important companies.

Reading the News

"Nasdaq slips" means the tech-heavy index fell slightly. "S&P hits record high" means the basket of 500 large US stocks reached an all-time high. Indices are the language of daily financial headlines.

Summary

• An index tracks a group of stocks as a single measure
• Famous indices: S&P 500, Dow, NASDAQ, FTSE 100
• They measure performance, benchmark portfolios, and feed index funds
• Most are weighted by market capitalization
• Indices let you gauge market direction at a glance

Next Lesson

Now let's get practical: how do you actually place a buy or sell order?