last year the number of students who graduated with a driving licence reached 200000,an ____of 4000

last year the number of students who graduated with a driving licence reached 200000,an ____of 4000
last year the number of students who graduated with a driving licence reached 200000,an ____of 4000

last year the number of students who graduated with a driving licence reached 200000,an ____of 4000
...an (increase) of 4000.
去年毕业时已获得驾照的学生达到了20万人,增长了4000人.

average
指的是每年平均增长