To help you understand, here is a basic overview of some of the forces that cause this volatility. Read on to learn about the way the stock market works and how stock prices are set.

The Stock Market Is an Auction

The stock market is, in essence, an auction, with one party wanting to sell its ownership in a particular company and another party wanting to buy ownership. When the two parties agree on a price, the trade is matched, and that becomes the new market quotation for the stock. The buyers and sellers can be individuals, corporations, institutions, governments, or asset management companies that are managing money for private clients, mutual funds, index funds, or pension plans. In many cases, you won’t have any idea who is on the other side of the trade. The number of shares traded is called the “trading volume,” and it can indicate how “hot” a particular stock is or how much interest there is in it from other investors. It can also give traders an idea of how easy it will be to get into or out of a position in a certain stock.

Supply and Demand

Stock prices are affected by supply and demand. Because the stock market functions as an auction, when there are more buyers than there are sellers, the price has to adapt, or no trades will be made. This situation tends to drive the price upward, increasing the market quotation at which investors can sell their shares and enticing investors to sell when they had previously not been interested in selling. On the other hand, when sellers outnumber buyers, and there is less demand, whoever is willing to take the lowest bid sets the price, resulting in a race to the bottom.

What Influences Buyers and Sellers

On a typical day, the value of shares of stock doesn’t move much. You’ll usually see prices go up and down by a percentage point or two, with occasional larger swings. But sometimes, events can occur that cause shares to rise or fall sharply.

External Events

Increased trading could be caused by an earnings report that shows good or bad financial news. It may be a major financial news event such as an interest-rate hike, or it could even be a natural disaster such as a hurricane that is likely to have far-reaching consequences. Any of these events could trigger a reaction in the market, causing investors to rush to sell or buy. These reactions could be based on emotion or be the result of a calculated decision; either way, they can affect the price of the stock.

Investor Analysis

Investing style can vary widely and affect the sale of stock. For example, suppose a particular company issues a poor earnings report. Some holders of that company’s stock may panic, selling their shares and driving the price down as supply exceeds demand. On the other hand, some investors may see the bad news as temporary and thus spot an opportunity to scoop up shares at a discount until the value of the stock rises again. Speculators—those who buy and sell not based on a company’s intrinsic value but on some other metric—can drive stock prices to extremes. Contrast them with investors, who care only to purchase stock at a discount from its worth, with the confidence that it will grow in value over time.