Hi Fudla, your essay is actually clear and very informative. I like the way you push your effort to write some advanced vocabularies, which will not escape the attention of the examiner. However, those advanced vocabularies are not adequate yet, because the proportion is not balanced between advance and intermediate one. For instance, change = alter, approximately (you wrote it twice) = roughly, and many other possibilities to vary your range of vocabularies. Somehow, there are still some grammatical issues and few spelling mistakes in which penalizing your final score. Later on, try to be more aware of those problems. Now, for a breakdown of your grammar errors, with corrections applied.
four age group
four age groups
there was no significant changes
there were no significant changes
Stood at 15% for the youngest group, and a quarter for people aged 24-34.
missing subject, 2000 stood at 15% for the youngest group and a quarter for people in the age group of 24-34.
Although 44-54 age group remained stabil, adults aged 34-44 saw a reverse
Although the age group of 44-54 remained stable, adults ranging from 34 to 44 saw a reverse. (I modify the second clause to make a variation)
It was dropped gradually
it was gradually dropped..
occured
occurred
All of the rate were
All of the rates were...
Followed by the steady rose until all of them peaked around 5-8% from their first figure.
(missing subject)
It was followed by the steady rose until all of them peaked around 5-8% from their initial figure.