What is Trading Volume? (Plain English Definition)
Definition: Trading volume is the total number of shares of a security that are bought and sold during a specific time period, usually one day.
Trading Volume Explained Simply
Trading volume represents the total number of shares that change hands during a given period. When someone buys 100 shares and someone else sells 100 shares, that transaction adds 100 to the volume count. Daily volume is the most commonly referenced timeframe, but volume can also be measured hourly, weekly, or monthly.
Volume is a key indicator of market interest and liquidity. High-volume ETFs have many active buyers and sellers, resulting in tight bid-ask spreads and easy execution. Low-volume ETFs may have fewer participants, wider spreads, and more difficulty executing large orders without moving the price.
Volume patterns can provide useful information. A sudden spike in volume may indicate significant news or a shift in investor sentiment. Steadily declining volume might suggest waning interest in a particular ETF. For index ETFs, volume tends to increase during periods of market stress as investors rush to buy or sell. The SPDR S&P 500 ETF (SPY) is the world's most heavily traded security, regularly exceeding 80 million shares per day.
Trading Volume Example
SPY averages over 80 million shares traded per day, meaning you can buy or sell virtually any amount instantly. A small thematic ETF might average only 20,000 shares per day. If you want to invest $50,000 in the small ETF (about 1,000 shares at $50 each), your order represents 5% of the average daily volume. Such a large relative order could move the price against you, costing you extra money through market impact.
Why Trading Volume Matters for ETF Investors
Volume is a practical indicator of how easily and cheaply you can trade an ETF. Higher volume generally means lower transaction costs and better execution quality. For ETF investors who trade infrequently (buy-and-hold approach), volume is less critical. For those who trade more actively, it is an essential consideration. For ETF investors, checking daily volume before investing helps avoid liquidity issues. As a general guideline, prefer ETFs with average daily volume above 100,000 shares for smooth trading. For very large purchases, ETFs with volume above 1 million shares per day provide the best execution. Remember that an ETF's tradability depends not only on its own volume but also on the liquidity of its underlying holdings.
Trading Volume vs Liquidity
| Trading Volume | Liquidity |
|---|---|
| Trading volume is the total number of shares of a security that are bought and sold during a specific time period, usually one day. | See full definition of Liquidity |
While trading volume and liquidity are related concepts, they serve different purposes in the world of ETF investing. Understanding both terms helps you make more informed decisions about which funds to include in your portfolio and how to evaluate their performance.
Related Terms
Deepen your understanding of ETF investing by exploring these related concepts:
Liquidity
Liquidity refers to how quickly and easily an investment can be bought or sold without significantly affecting its price.
Bid-Ask Spread
The bid-ask spread is the difference between the highest price a buyer will pay and the lowest price a seller will accept for a security.
Assets Under Management (AUM)
Assets under management (AUM) is the total market value of all investments held within a fund, representing its overall size.
Market Maker
A market maker is a firm that continuously quotes both buy and sell prices for a security, providing liquidity and facilitating smooth trading.
Illiquid
An illiquid investment is one that cannot be easily bought or sold without significantly affecting its price, often due to low trading volume.
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