Spot premium refers to the discount on the distant month, which is mainly caused by the market's relative optimism about the recent month or pessimism about the distant month. Futures premium is a kind of distant lunar water. Generally speaking, the normal structure of futures is premium structure, and the futures price of far month = futures price of near month+storage cost (interest), so the premium of far month increases. However, in reality, regression curves often appear. On the one hand, the market has poor expectations for the future. For example, if the economy is not good, prices will fall in the future. Or the demand has suddenly improved recently, the spot is in short supply, and the price has skyrocketed in recent months. Another situation is the phenomenon of forced warehousing, which leads to insufficient warehouse receipts in recent months, but it is relatively rare.