Basis is the difference between the spot price and the futures price of a specific commodity at a specific time and place. Its calculation formula is:

Basis = spot price-futures price.

If the spot price is lower than the futures price, the basis is negative; The spot price is higher than the futures price and the basis is positive.

Therefore, when the difference between the spot price and the futures price becomes larger and larger, the basis will be positive and the value will become larger and larger, and the basis will strengthen at this time.