Lesson 4 of 31 · Zero to reading a chart

What Is a Stock Index? The Nasdaq Didn't Fall

An exchange is a place; an index is a list of companies turned into one number - and most listed companies are not on any list.

The Nasdaq fell two percent. You have heard that sentence a hundred times. What exactly fell?

Not the Nasdaq. The Nasdaq did not fall. A list of a hundred companies did.

Last time you learned the Nasdaq is a network. The marketplace where shares change hands. A marketplace does not have a price. It cannot go up or down.

So the word is doing two jobs, and nobody tells you. There is the Nasdaq, the exchange. The place. And there is the Nasdaq one hundred, an index. A list.

Here is what an index actually is. Somebody picks a group of companies.

Then, every second of the trading day, their prices are combined into one number. That number is the index. It is a summary. Nothing more.

The Nasdaq one hundred is a list of a hundred big companies. All of them listed on that exchange. The S and P five hundred is five hundred large American companies. The Dow is thirty. Different lists, different lengths, same idea.

So when the news says the market fell, they mean one thing. One of those lists produced a smaller number today than yesterday. That is the whole sentence.

Here is a real large company on a real day. It is in two of those lists. When the lists moved, this moved with them. It is part of the number.

And here is a company on the exact same day. It is in none of those three lists. Nothing in the news that evening described this chart. The market did not include it.

That is worth sitting with. Most listed companies are not in any of those lists. Thousands of them. Somebody tells you what the market did today. They have told you about a few hundred companies. And said nothing about the rest.

An exchange is a place. An index is a list turned into one number. They share a name. They are not the same thing.

Here is the mistake. Somebody hears the market is up. They open a chart, and cannot understand why their stock is down. Their stock may not be in the list. The list was up. The stock was down. Both true. They were never measuring the same thing.

Next time you hear the market, ask one question. Which list?

Check yourself

Can you buy the Nasdaq index?

No. It is a list, not a company.

"The S&P fell" - what actually fell?

The combined number of 500 companies.

Is every listed company in one of those lists?

No. Most are not.

Next lesson: Where a price actually comes from.

For learning only. Not financial advice, not signals, not stock picks.