Quote from J-Blaze:
I am pretty sure that the first part and the third part is incorrect.. the 2nd part is correct.. here is the breakdown
#1 -INCORRECT "if you buy a contract from someone that is selling one to enter a position AND you are buying to enter a position then yes it goes up by one"
-if someone sells to open.. that equals +1 to open interest
-if you buy to enter a postion.. that equals +1 to open interest
-the total is +2 to open interest.
#2 - CORRECT "If you buy from someone that had already bought and is closing a position and you are opening a position then it stays the same"
-if that 'someone' closes their position.. then that is a -1 to open interest
-if you buy to open a contract. that is +1 to open interest.
-this scenario would make no change to open interest. you are correct with this one
#3 - If you are buying to close from someone selling to close then it goes down by one. You never know when you buy which will happen.
- if you are buying to close.. open interest will be -1 as a result
-if someone is selling to close.. then open interest will be -1 as a result
-open interest will be -2 as a result of your third scenario.. not flat (0)
again.. like I noted in my first response (I had little time to spell this out.. now I do).. the options exchange will act as a market maker when buyers and sellers do not line up equally. this provides liquidity in the market and assures people that they will always be able to open or close their contracts.
this is the way it works. not like you described.
If you think I'm incorrect about any of this.. please correct me.. I'm learning like most of us. I"m pretty sure I'm right. I got that information from multiple sources and from people who do this successfully for a living.
Open Interest is a count of Open Contracts not open positions. Which is why what I said and MTE said is correct. A contract for anything covers 1 buyer and 1 seller. If you write a contract to buy a house, you don't need a second contract for the seller to sell it. The one contract includes the buyer's commitment and the seller's commitment.
If you buy to open from someone selling to open (going short) then OI increases by 1 because only 1 new contract is created.
When you buy to open from someone that is selling to close. Then OI doesn't change since a contract was neither created nor completed it just changed hands.
When you buy to close from someone selling to close the contract is considered complete and reduces OI by 1.
Lets take a Call Option contract for example. If I decide to write a call option (sell one to open) and you decide to buy it you now hold the contract I wrote. You do not need to create a whole new contract. I now have the obligation to sell my underlying equity at the strike price of the option and you have the option to buy my underlying equity at the designated stock. Since only 1 new contract was created OI is increased by 1.
Now you decide to sell the same option (closing your position) to someone else that wants to open a position. The contract that I wrote will simply change hands to the new buyer and no new contract is needed so OI stays the same.
Now that guy decides to sell the option to close his position and I decide I want to close my position and buy back my contract. Since there is no longer a buyer or seller for this option the contract is closed and OI drops by 1.
I hope that makes more sense to you. OI is a count of contracts not positions.
, but because most forums have a few posters that bring the most wisdom (the ol' 80/20 rule).