Repetition is used because they state several times that they would do anything. And the other two are not rhetorical devices anyway.
Answer:
There are real differences in the populations in different countries. Demographics are particularly important - that's things like average age, or where people live.
Explanation:
But not all testing data is the same - some countries record the number of people tested, while others record the total number of tests carried out (many people need to be tested more than once to get an accurate result).
