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What is a Block Trade?
block trade
block trade

One hundred is a lot of shares. Literally, when trading stock one “lot” is defined as 100 shares. A round lot is any number of shares evenly divisible by 100, while any other amount is considered an “odd lot.” Block traders do not deal in lots of shares. They operate on a scale several orders of magnitude larger.

What Is a Block Trade?

Simply put, a block trade is the exchange of a very large number of financial assets.

Neither Congress nor the SEC have issued a legal definition of a block trade, and the term is often used casually. Most markets, however, have their own rules defining what constitutes a “block.” In practice most people default to the New York Stock Exchange’s Rule 127.10. This defines a block trade as one which involves at least 10,000 shares of stock or a market value of $200,000, whichever is less. Generally, this means that most investors consider a block trade as any exchange involving at least 10,000 units of the traded asset or at least $200,000 worth of that asset. For example, that could be 10,000 shares of stock or $200,000 worth of bonds.

Most block trades involve considerably larger amounts than this. Furthermore, while investors can technically conduct block trades on any financial market, most block trades involve either shares of stock or bonds. As a result, most block trading concerns the equity and debt markets.

Block trading is almost always conducted by institutional investors such as funds or corporations. Mainly, this is because the volumes involved price all but the wealthiest individual investors out of the practice.

Why Do Block Trades Matter?

block trade
block trade

From the traders’ point of view, block trading is a way to move large amounts of a security without its market price changing during the process. If a hedge fund, for example, wanted to sell 1 million shares of a given company, doing so in parcels of 5,000 shares apiece would take time. During the course of those many trades (200 to be exact) the price of that stock could move, narrowing their expected profit margin. This is not to mention any potential issues involved with finding that many buyers for the same stock in a short amount of time.

Block trading eliminates that risk, letting the fund sell all 1 million of its shares simultaneously and at a single price.

Block Trades and Market Volatility

From a market standpoint, block trades can also promote instability. Sudden, large movements in a given asset can cause sudden price swings. This is bad enough when it promotes volatility in the market. It’st far worse given that the price movement may be unrelated to that security’s value.