decrease
101plunge of the dollar — decrease in the value of the dollar …
102qualitative decline — decrease in quality …
103quantitative decline — decrease in quality, wane of quality …
104slow down the rate — decrease the pace …
105slow up — decrease in speed …
106wage erosion — decrease in the value of the salary …
107fall off — decrease The number of tourists to visit the island has fallen off recently …
108slack off/up — decrease in intensity or speed. → slack …
109spiral down/downward — decrease continuously. → spiral …
110step something down — decrease voltage by using a transformer. → step …