Hi bongbang, there are several suggestion for your essay, I hoped that you do not mind.
The line graph illustrates
I personally think that "illustrates" is inappropriate to explain about your line chart. I think word "illustrate" is appropriate when we are going to explain about process or map. As either line charts or other graphs are contained by figures. So, could you imagine it, how to illustrate figure?. Therefore, I thought it is more appropriate we use illustrates to explain Map or Process rather that explain line charts.
after 2 years
According to several IELTS writing books. We are suggested to write 1-10 by word. For example, if we want to write "2" in essay, it should be "two".Missed Spelling =
end point comparing to the begining .
it should be = end poin comparing to the beginning
there was adramatical
it should be = there was a dramatic
What's more, try to make essay in 150-200 words, I believe your IELTS score will be encreased.KEEP STUDY, KEEP SPIRIT.