Nouns used when describing trends
decline
decrease
dip (a momentarily small drop in the level of something)
drop
fall
fluctuation (= an irregular rising and falling in number or amount; a variation)
growth
increase
peak (= the highest point)
rise
slump (= a severe or prolonged fall in the price, value, or amount of something)
variation (= a change or difference in condition, amount, or level)