What is Ratchet Effect?

Legal Definition
A ratchet effect is an instance of the restrained ability of human processes to be reversed once a specific thing has happened, analogous with the mechanical ratchet that holds the spring tight as a clock is wound up. It is related to the phenomena of featuritis and scope creep in the manufacture of various consumer goods, and of mission creep in military planning.

Ratchet effect in sociology: "Ratchet effects refer to the tendency for central controllers to base next year's targets on last year's performance, meaning that managers who expect still to be in place in the next target period have a perverse incentive not to exceed targets even if they could easily do". (Bevan and Hood 2006, p. 521)
-- Wikipedia
Legal Definition
The inclination to be influenced by an earlier level of a variable (factor). For instance, a workers? currently salary satisfaction depends on how it measures up to a past salary.