Stock exchanges are set up to assist brokers and other specialists in coordinating bid and ask prices. The bid price is the amount that a buyer is willing to pay for a particular security, while the asking price is the amount that a seller will take for that security.

The asking price it is always a little higher than the bid price. The difference between the bid and ask prices is what is called the bid-ask spread, and this difference represents a profit for the broker or specialist handling the transaction.

Liquidity Impact on Bid-Ask Spreads

There are several factors that contribute to the difference between the bid and ask prices. The most evident factor is the security's liquidity. This refers to the volume or number of shares traded on a daily basis. Some stocks are traded regularly, while others are only traded a few times a day.

The stocks and indexes that have large trading volumes will have narrower bid-ask spreads than those that are infrequently traded. When a stock has a low trading volume, it is considered illiquid because it is not easily converted to cash. As a result, a broker will require more compensation for handling the transaction, accounting for the larger spread.

Volatility and Bid-Ask Spread 

Another important aspect that affects the bid-ask spread is volatility. Volatility usually increases during periods of rapid market decline or advancement. At these times, the bid-ask spread is much wider because market makers want to take advantage of—and profit from—the change. When securities are increasing in value, investors are willing to pay more, giving market makers the opportunity to charge higher premiums. When volatility is low, and uncertainty and risk are at a minimum, the bid-ask spread is narrow.

Stock Price Impact

A stock's price also influences the bid-ask spread. If the price is low, the bid-ask spread will tend to be larger. The reason for this is linked to the idea of liquidity. Most low-priced securities are either new or are small in size. Therefore, the number of these securities that can be traded is limited, making them less liquid.

Ultimately, the bid-ask spread comes down to supply-and-demand. That is, a higher demand and tighter supply will mean a lower spread. Today, with the help of technology, finding a buyer or seller can be done much quicker, helping make supply-and-demand dynamics much more efficient.

Types of Orders

When a buyer or seller goes to place an order, there's a variety of orders that can be placed. This includes a market order, which, when placed, means the party will take the best offer. Then there's a limit order, which puts a limit on the price one is willing to do the transaction. A limit order will only be completed if that price is available. Meanwhile, a stop order is a conditional order, where it becomes a market or limit order when a particular price is reached. It can't be seen by the market otherwise, unlike a limit order, which can be seen when placed.

The bid-ask spread can say a lot about a security, meaning you should be aware of all the reasons that are contributing to the bid-ask spread of a security you are following. Your investment strategy and the amount of risk that you are willing to take on may affect what bid-ask spread you find acceptable.