How much less old cars will be bought when the new car comes on the market than when it first comes on the market?

In many stores in 4S, especially when talking about the difference between new cars and old cars, salespeople often introduce new cars with skylights, multi-function steering wheels, audio-visual entertainment navigation, sports kits and so on. Almost the main introduction will focus on the visible part of the new model. As for which configurations have been reduced, sales people tend to downplay them, such as two airbags missing and no body stability system as standard. In fact, more invisible configurations are often ignored intentionally or unintentionally in understatement.