Open Interest Is The Glue That Holds A Market Together
Open interest is the glue that holds a market together. When an index trades in the same area for weeks, contracts pile up at those strikes and never get closed. That accumulation builds into an enormous ball of risk sitting under the market. It is the reason most days feel orderly. Dealers holding the other side of all those contracts have obligations. They hedge as price approaches a strike and unwind as it moves away, and that mechanical activity anchors the tape whether anyone notices or not. Roll your chart back into any area where the market spent real time and you will find a proverbial crap load of open interest sitting there. Trade in that neighborhood is solid, more predictable, and it behaves the way you expect a market to behave. Now take the glue away This week the S&P 500 blew through its weekly expected move and kept