The so-called ratchet effect refers to the irreversibility of people’s consumption habits after they are formed, that is, it is easy to adjust upward but difficult to adjust downward. Especially in the short term, consumption is irreversible and its habitual effect is large. This habit effect makes consumption depend on relative income, that is, relative to one's past peak income. Consumers are prone to increase consumption as their income increases, but are less likely to reduce consumption as their income decreases, resulting in a short-term consumption function with a positive intercept. This characteristic is called the ratchet effect.