Describing graphs is a popular task in the IELTS exam and students are expected to come up with sentences such as:
The rate of unemployment fell dramatically after 1983..
The rate of inflation peaked in 1987 before declining gradually…
What you need to think about is not only the verb (fell, declined, rose, increased) but also the adverbs which go with the verbs (slowly, gradually, sharply).
Here’s a page doing just what we want from Hong Kong Polytechnic University here.