If you look at the band 7 description for 'lexical resource' (vocabulary), you'll see the words 'range' and 'flexibility'. You need to use a range of vocabulary in a flexible way.
But how can we demonstrate 'range' in such a short piece of writing? And what does 'flexibility' really mean in this context?
Let's look at two aspects of my most recent line graph answer.
- average daily expenditure / daily spending / spent... per day
- types of traveller / international visitors / travellers / people visiting / those visiting
- holidaymakers / tourists / vacationers
- friends or relatives / relations or friends / loved ones
- spent the most
- spent the least
- spent an average of
- spent around
- spent less than
- spent roughly
- spending was at its highest
- spending increased dramatically
- spending suddenly fell
- spending had risen to approximately
For me, paraphrasing is probably the best way to demonstrate 'range' and 'flexibility'. You are using a range of vocabulary items and your English is 'flexible' because you are able to describe the same thing in a number of different ways.
Repetition is interesting, especially because most IELTS students see it as a bad thing. This is not always true!
If you're describing a graph that shows spending, it's almost impossible to avoid repetition of the words 'spent', 'spending' and 'expenditure'. However, if you use these key words in a variety of contexts (i.e. with different words around them), I think you are demonstrating 'flexible use'. You are showing that you are able to use the same word in a number of different ways. I would also argue that you are demonstrating 'control' or 'precision' if you can do this without making mistakes; repetition is not necessarily as easy as it looks!