In 2015 sales of all 3 types of fast food increased dramatically.
This is a common error. Unfortunately there is no information about change in 2015, only from 2005 to 2015:
If you are not specific about the time frame then your reporting of data will be inaccurate and you will receive a low score in IELTS for Task Achievement.
Before you write, decide exactly when the change happened and design a suitable time expression. These are the most commonly used:
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