Open Interest

Open Interest (OI) is the number of contracts outstanding in the marketplace. Open Interest only applies to futures and option contracts. Changes in open interest either confirms price action or acts as a warning of a potentially weakening trend.A hypothetical situation is given next to help grasp the concept of Open Interest:* A new futures contract expiration month is opened for trading. Currently, no one has bought or sold a futures contract.* A trader (Trader #1) buys a futures contract, but in order for this to happen, someone has to sell that trader the future. Therefore, for every buyer there is an equal and opposite seller (Trader #2). When this transaction occurs, the open interest is increased from zero to one. There is now one contract outstanding in the marketplace.* Trader #3 decides to sell a future and subsequently another trader (Trader #4) has to buy that futures contract; therefore, open interest is now at two.* Trader #1 goes to the marketplace and sells his/her futures contract. Trader #3 decides to buy back his/her short future. After the transaction takes place, Trader #1 no longer owns a futures contract. Similarly, Trader #3 no longer owns a futures contract. Effectively, the marketplace has one less futures contract outstanding. The open interest went down to one.Generally open interest increases over the life of the futures contract (note: futures contracts expire, same with options). When futures contract months or quarters transition from one month or quarter to the next month or quarter, the future closest to expiration (called the "front month") decreases in open interest and the next futures contract (called the "back month") increases. Learning about Open Interest is important, but using it to help futures or options trading is better. Interpreting Open Interest is up next.Interpreting Open InterestOpen Interest is a helpful tool in analyzing the strength of a price move. There are four main interpretations of Open Interest:* If price increases and Open Interest increases, then their is strength behind the price move higher.* If price decreases and Open Interest increases, then their is strength behind the price move lower.* If price increases and Open Interest decreases, then their is weakness behind the price move higher.* If price decreases and Open Interest decreases, then their is weakness behind the price move lower.Analyzing Open Interest is a helpful tool in an options or futures trader's toolbox for determining the strengths and weaknesses of price trends