Open interest (also known as open contracts or open commitments) refers to the total number of derivative contracts, like futures and options, that have not been settled in the immediately previous time period for a specific underlyingsecurity. A large open interest indicates more activity and liquidity for the contract.[1]
For each buyer of a futures contract there must be a seller. From the time the buyer or seller opens the contract until the counter-party closes it, that contract is considered 'open'.
Use of Open Interest in Technical Analysis
Many technical analysts believe that a knowledge of open interest can prove useful toward the end of major market moves. For some option traders, open interest indicates the intensity of trading in a financial instrument. If open interest increases suddenly, it is likely that new information about the underlying security has been revealed, which may indicate a near-term rise in the underlying security's volatility. However, neither an increase in volatility nor open interest necessarily indicate anything about the direction of future price movements. A leveling off of open interest following a sustained price advance is often an early warning of the end to an uptrending or bull market.
Technical analysts view increasing open interest as an indication that new money is flowing into the marketplace. From this assumption, one could conclude that the present trend will continue. Analogously, declining open interest implies that the market is liquidating, and suggests that the prevailing price trend is coming to an end.
However, according to the definition of open interest in this entry, a change in open interest indicates a difference in the number of buyers and sellers of a financial instrument. Like volatility, it has no directional component, it is just a tally of unsettled contracts.
For example, if trader X buys 2 futures contract from trader Y(who is the seller), then open interest rises by 2.
If another trader A buys 2 futures contracts from trader B, then the open interest rises to 4. Now, if trader X unwinds his position and the counter party is either Y or B, then the open interest in the system will reduce by that quantity.
But if X unwinds his position, and the counter party is a new entrant, say C, then the open interest will remain unchanged. This is because while X has squared off his position, C’s position is still open. The level of outstanding positions in the derivatives segment is one of the parameters widely tracked by the market.
The Importance of Open Interest
Open interest is a concept all option traders need to understand. Although it is always one of the data fields on most option quote displays - along with bid price, ask price, volume and implied volatility - many traders ignore open interest. But while it may be less important than the option's price, or even current volume, open interest provides useful information that should be considered when entering an option position.
First, let's look at exactly what open interest represents. Unlike stock trading, in which there is a fixed number of shares to be traded, option trading can involve the creation of a new option contract when a trade is placed. Open interest will tell you the total number of option contracts that are currently open - in other words, contracts that have been traded but not yet liquidated by either an offsetting trade or an exercise or assignment.
For example, say we look at Microsoft and open interest tells us that there have been 81,700 options opened for the March 27.5 call option. You may be wondering if that number refers to options bought or sold. The answer is that you have no way to know for sure.
When you buy or sell an option, the transaction needs to be entered as either an opening or a closing transaction. If you buy 10 of the Microsoft March 27.5 calls, you are buying the calls to 'open'. That purchase will add 10 to the open interest figure. If you wanted to get out of the position, you would sell those same options to 'close' and open interest would then fall by 10.
Selling an option can also add to the open interest. If you owned 1,000 shares of Microsoft and wanted to do a covered call by selling 10 of the March 27.5 calls, you would be entering a sale to open. Since it is an opening transaction, it would add 10 to the open interest. If you later wanted to repurchase the options, you would enter a transaction to buy to close. Open interest would then decrease by 10.
Things get a little more complicated if the options you trade are not created by the transaction, but instead the other side is taken by someone doing a closing transaction. For example, if you are buying 10 of the Microsoft March 27.5 calls to open, and you are matched with someone that is selling 10 of the Microsoft March 27.5 calls to close, then the total open interest number will not change.
So when you are looking at the total open interest of an option, there is no way of knowing whether the options were bought or sold - which is probably why many option traders ignore open interest altogether. However, you shouldn't assume that the open interest figure provides no important information.
One way to use open interest is to look at it relative to the volume of contracts traded. When the volume exceeds the existing open interest on a given day, this suggests that trading in that option was exceptionally high that day. Open interest can help you determine whether there is unusually high or low volume for any particular option.
Open interest also gives you key information regarding the liquidity of an option. If there is no open interest for an option, there is no secondary market for that option. When options have large open interest, it means they have a large number of buyers and sellers, and an active secondary market will increase the odds of getting option orders filled at good prices. So, all other things being equal, the bigger the open interest, the easier it will be to trade that option at a reasonable spread between the bid and ask.[2]
Benefits of Monitoring Open Interest
By monitoring the changes in the open interest figures at the end of each trading day, some conclusions about the day’s activity can be drawn.
Increasing open interest means that new money is flowing into the marketplace. The result will be that the present trend (up, down or sideways) will continue.
Declining open interest means that the market is liquidating and implies that the prevailing price trend is coming to an end. A knowledge of open interest can prove useful toward the end of major market moves.
A leveling off of open interest following a sustained price advance is often an early warning of the end to an uptrending or bull market.
Open Interest - A Confirming Indicator
An increase in open interest along with an increase in price is said to confirm an upward trend. Similarly, an increase in open interest along with a decrease in price confirms a downward trend. An increase or decrease in prices while open interest remains flat or declining may indicate a possible trend reversal.
The relationship between the prevailing price trend and open interest can be summarized by the following table:[3][4]
| Price | Open Interest | Interpretation |
|---|---|---|
| Rising | Rising | Market is Strong |
| Rising | Falling | Market is Weakening |
| Falling | Rising | Market is Weak |
| Falling | Falling | Market is Strengthening |
1. If prices are rising and open interest is increasing at a rate faster than its five-year seasonal average, this is a bullish sign. More participants are entering the market, involving additional buying, and any purchases are generally aggressive in nature.
2. If the open interest numbers flatten following a rising trend in both price and open interest, take this as a warning sign of an impending top.
3. High open interest at market tops is a bearish signal if the price drop is sudden, since this will force many weak longs to liquidate. Occasionally, such conditions set off a self-feeding, downward spiral.
4. An unusually high or record open interest in a bull market is a danger signal. When a rising trend of open interest begins to reverse, expect a bear trend to get underway.
5. A breakout from a trading range will be much stronger if open interest rises during the consolidation. This is because many traders will be caught on the wrong side of the market when the breakout finally takes place. When the price moves out of the trading range, these traders are forced to abandon their positions. It is possible to take this rule one step further and say the greater the rise in open interest during the consolidation, the greater the potential for the subsequent move.
6. Rising prices and a decline in open interest at a rate greater than the seasonal norm is bearish. This market condition develops because short covering, not fundamental demand, is fueling the rising price trend. In these circumstances money is flowing out of the market. Consequently, when the short covering has run its course, prices will decline.
7. If prices are declining and the open interest rises more than the seasonal average, this indicates that new short positions are being opened. As long as this process continues it is a bearish factor, but once the shorts begin to cover, it turns bullish.
8. A decline in both price and open interest indicates liquidation by discouraged traders with long positions. As long as this trend continues, it is a bearish sign. Once open interest stabilizes at a low level, the liquidation is over and prices are then in a position to rally again.