S&P 500

Definition

The S&P 500 is a stock market index containing 500 of the largest publicly traded companies in the United States. It's weighted by market value, so bigger companies have more influence. The index has been tracked since 1957 and is considered the best overall indicator of U.S. stock market health and performance. Most professional investors use it as a baseline for comparing returns.

Why it matters

The S&P 500 has delivered roughly 10% average annual returns over the past century, including recessions and crashes. This makes it a reliable proxy for the U.S. economy's growth. If you can't beat the S&P 500, you should own the S&P 500 instead of trying, which is why S&P 500 index funds are so popular. The companies in it include household names like Apple, Microsoft, Amazon, and Berkshire Hathaway, so you're getting exposure to real businesses that drive the economy.

Quick example

You invest $50,000 in an S&P 500 ETF. You own a slice of 500 companies. Apple makes up about 7% of your holding, Microsoft about 6%, and so on. An $80,000 annual return from the S&P 500 index fund over 15 years (at 10% average returns) grows your $50,000 to roughly $208,000. That's not flashy, but it's reliable and requires zero stock-picking skill.

The bottom line

Knowing what S&P 500 means helps you make better day-to-day money decisions. It makes rates, account options, and tradeoffs easier to compare.