"the percentage of the changes" vs. "the percentage of changes" and use of an article "the"?

Question

I write the following two statements from the graph.

Statements

1. The given line graphs illustrate the percentage of the change in usage of the three electrical appliances.
2. The given line graphs illustrate the percentage of change in usage of the three electrical appliances.

Questions

Q.1) Which statement is correct, first or second? and explain the reason.

Q.2) In the above statements, should I write or not an article "the" before three electrical appliances and before usage? and explain the reason.

Answer 1

Neither, really.

Percentage change is the change, expressed as a percentage of the original amount. In the case of the refrigerator the original amount is 0, so the percentage change is actually infinite...

Percentage of change is not a common idiom, and is likely to be confused with percentage change. So I wouldn't use this either. Adding "the" doesn't help.

I'd say "These graphs show the growth in usage...."

You would use "the" if you had previously been discussing these three appliances. They are "the" appliance that I am discussing in this article. You wouldn't use "the" if your article was about appliances in general, changes in quality of life or something else. In most cases "the" can probably be omitted.

Answer 2

The correct term is percentage change. A graph or visual would almost certainly use this term. See this ngram comparing it against your suggestions. You will see that "percentage of change" is sometimes used, but rarely.

I would say you do not need to use an article with the three items on your chart. Visual representation of data is most successful when the text is brief. Also, the data behind a chart would usually not use articles, as it affects alphabetical ordering.