How is the share price formed on the stock exchange? We do it

2022年12月6日

You already know that the stock exchange is a one-stop place to buy or sell stocks, whether you are a novice investor or a seasoned professional. But even if you don't trade stocks, you will still "come" to the stock exchange to find out stock prices.

Let's find out how the exchange price of a stock is formed. Regardless of what country the stock exchange is in, the rules for determining the price are similar for everyone. Let us understand how it works, as always, with the help of our imagination.

Imagine a large rack of books. Each book has a name on the cover: Apple, Facebook, Amazon, etc. Let's take one of the books, let's say Facebook, and open it. We will see only two pages, and they are both blank. On the left page we will record buyers' orders to buy shares, and on the right page we will record sellers' orders, respectively, to sell shares. So, every day the exchange, when it opens trading, essentially opens such a "book" and records every bid it receives.

What should be written in the order?

First of all, there must be an abbreviated name of the stock, or, in professional slang, the "ticker," to understand which book to get off the shelf. For example, Facebook shares have a ticker consisting of two letters FB, while Apple shares have four letters - AAPL.

Second, the order must indicate the direction of the transaction, i.e. "buy" or "sell". This is how the exchange understands whether to record the incoming information on the left or on the right page of the book.

Third, the order must indicate the price per share, so that the exchange can sort the orders in descending order of price from top to bottom.

Fourth, the order must specify the volume in lots, that is, how many lots of shares we want to buy or sell. To clarify: Shares on the exchange are not traded by the piece, but by the lot. The lot size is set by the exchange. One lot may be equal to one share, or a hundred, a thousand, or even ten thousand shares (depending on the specific share). This is really handy because the price of one share can be equal to, for example, the price of your computer (then 1 lot may be equal to 1 share), and sometimes 1 share may be worth as much as a box of matches (then 1 lot may be equal to a thousand shares). Why "may be"? The specific rules for determining the lot size depend on the laws of the country and the exchange itself. For example, on the New York Stock Exchange (NYSE), the usual size of 1 lot is equal to 100 shares.

So, let's return to our example. Suppose we want to buy shares of FB at a price of $100 per share in the amount of 10 lots. Then the exchange will record the following on the left side of the FB book:
100$ 10

Then there is a seller who wants to sell FB stock at $110 per share in an amount of 20 lots. Then this is what the exchange will record in the right side of the book:
110$ 20

Then there is a buyer who wants to buy FB stocks at $115 per share in an amount of 25 lots. The entry on the left side of the FB book will look like this:
115$ 25



And now comes the interesting part.
Did you notice that the $115 price in the last buy order is higher than the single sell order of $110? That means the buyer is willing to make a deal at a price even higher than what the seller is offering. So at what price and what volume will the deal end up being made?

Please wait for the next post.