ELI5: Explain Like I'm 5

Financial market efficiency

Okay, so imagine you have a big jar of candy. A lot of people want to buy that candy from you. Some people are willing to pay a lot for it, while others don't want to pay as much.

The financial market is like this candy jar. It's a place where people buy and sell things like stocks, bonds, and other financial instruments. Just like the candy buyers, there are many people who want to buy these financial instruments.

When we talk about financial market efficiency, we are talking about how quickly and accurately the prices of these financial instruments reflect all the available information about them.

Let's say there's a company called ABC Corp. They are going to release their quarterly earnings report soon. This report will tell us how much money they made or lost in the last three months.

Before the report comes out, some people might think ABC Corp is doing really well and will make a lot of money. They might be willing to pay a high price to buy ABC Corp stock. Other people might think ABC Corp is doing poorly and won't make a lot of money. They might only be willing to pay a lower price for the stock.

But when the earnings report comes out, it will tell us exactly how much money ABC Corp made or lost. If they did well, the people who bought the stock for a high price will be happy, because the stock price will likely go up. But if they did poorly, those people will be unhappy, because the stock price will go down.

This is an example of the financial market reacting quickly and accurately to new information. Financial market efficiency is the idea that all available information is quickly and accurately reflected in the prices of financial instruments.

Of course, this doesn't always happen perfectly. Sometimes information is slow to spread, or people have different interpretations of the same information. But the goal of financial market efficiency is to make sure prices are as accurate as possible, so people can buy and sell with confidence.