Quote from Maverickz:
However I assume you might be talking about the Open Interest of an option. If so, the answer is: 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 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 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. [/B]
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.