when the basis shrinks from a negative number like 1 to a less negative number like 0 50 this change is known as a strengthening basis on the other hand when the basis shrinks from a larger positive number to a smaller positive number this is known as a weakening basis 
generally speaking a narrow basis is consistent with a very liquid and efficient marketplace whereas a wide basis is associated with a relatively illiquid and inefficient one nonetheless some variation between local cash prices and futures prices is normal and expected real world example of a wide basissuppose you are a commodities futures trader interested in the oil market you note that the local cash price for crude oil is 40 71 whereas the price of crude oil futures maturing in two months is 40 93 in this scenario you note that the basis between these two prices is relatively small at only 0 22 spot price of 40 71 minus futures price of 40 93 this narrow basis makes sense considering that the contract is heavily traded and there are only two months until the expiration of the contract looking farther into the future however you begin to find some contracts with a wide basis the same contract for delivery in nine months for example has a futures price of 42 41 this relatively wide spread of 1 70 could be due to many different factors for instance traders might be expecting the price of oil to rise as a result of decreased supply or increased economic activity no matter the reason the basis will almost certainly diminish as the contract date approaches 