Quote from Chagi:
This doesn't make sense to me. My understanding of options is that someone initially sells (writes) a put/call, which causes open interest to increase by 1. The option is then offered on the market (or sold at the bid to a MM), someone else can then come along and purchase at the ask (or put their own bid up I suppose).
So, that said, can you explain how it is that MMs would sell as many contracts as one wants when there is a buyer? Are the MMs then both liquidity providers and options writers in the market?
Actually, Open interest increases/decreases only in two cases.
1. If a buyer opens a new position and a seller opens a new position (open interest increases)
2. If a buyer is closing an existing position and a seller is closing an existing position (open interest decreases)
That's it. In other cases where one side is opening and the other is closing open interest will not change.
Option writer is anyone who sells an option - MM, retail trader, institutional trader and etc.
I think you misunderstand the concept of how options trade.
Selling (writing) an option is one transaction. I put in an order to sell a call and once someone buys it (MM or someone else) I have sold (written) a call. An option contract does not exist until there's a transaction between a buyer and a seller.
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