The change of futures price is closely related to the supply of commodities. If there is a shortage of a commodity in the spot market, the spot price is higher than the futures price, because traders all think that when the futures are due for delivery, the supply of the commodity will increase and the corresponding price will decrease, so the futures in recent months are usually higher than those in forward months.

But if this shortage disappears, it will return to the premium market. Through the change of this price, we can understand why the "basis" has been changing, which is actually determined by the relationship between supply and demand in the market and the expected psychological factors of traders.

Theoretically speaking, no matter how the prices of futures and spot change and how big the price gap is, one day, their prices will be equal. At this time, there is no long-term factor when the futures contract is due for delivery.