Open interest studies are available only on futures plotted on daily and weekly charts. John J. Murphy, Technical Analysis of the Futures Market, A Comprehensive Guide to Trading Methods and Applications, New York: New York Institute of Finance, A Prentice-Hall Company, 1986, 176-199. Open interest is the number of outstanding, or un-liquidated, futures contracts at the end of a trading day. Every time a contract is traded on the exchange floor, open interest is affected in one of three ways: it increases, decreases, or it stays the same. This information can help you interpret the relative strength or weakness of a market.Open Interest