In the Writing paper of the IELTS Academic Exam you must complete two tasks. In Task 1 you will be presented with some visual information such as a graph, table, chart or diagram. You have about 20 minutes to describe the data in your own words, writing at least 150 words. Adding value to your essay by commenting on the data shows that you are able to select and report the most important features and identify significance and trends. This will help you turn an average mark into a higher one. Let’s look at an example:

The sales of bread rolls increased from 300 in the first quarter to 500 in the second.

This is good writing. It’s grammatically correct and provides data to support the assertion that sales have increased. However, what if we add a comment?

The sales of bread rolls increased from 300 in the first quarter to 500 in the second, making them the highest-selling bakery product in the first half of the year.

The second example adds value by commenting on the data. It uses a participle clause to do so, though there are other ways.

The sales of bread rolls increased from 300 in the first quarter to 500 in the second, which made them the highest-selling bakery product in the first half of the year.

This example uses a relative clause, but there are other ways.

Bread rolls became the highest-selling bakery product in the first half of the year due to an increase from 300 in the first quarter to 500 in the second.

For some exercises on commenting on data, see the excellent IELTS Advantage Writing Skills by Richard Brown and Lewis Richards, published by Delta.