You have not inconvenienced me. Teachers and natives wishing to help learn as much from members questions as the members asking questions. the responder(s) have to think about their answers and hopefully not make too many mistakes.

have a good weekend.

Yes it is a general preference to say "or" to indicate either range range as per the dictionary definitions of "or"... But after seeing the full context. I think it would be better to use "to".

 In fact, in Britain now only about four TO five per cent of people live in rural areas and depend upon them; 

Four to five percent = a flexible range. From four to five and all ranges in between.

 In fact, in Britain now only about four or five per cent of people live in rural areas and depend upon them; 

FOUR OR FIVE percent = either 4 or five percent, I agree with you it is not clearly written.

It is not you who is confused it is the writer that has confused you, by not adequately proofreading her text, or the book writers proofreaders may have missed the obvious.

You may adjust my answer to take into account this new answer and the new information provided.

It is always best to provide the full context to receive correct and proper answers from anybody that is attempting to assist.

10/10 marks for an excellent observation well done.

Thank you, john! Now I can fully understand it!

You are right that I should have provided the full context in the first place rather than putting separate sentences in a roll to have misled you! I'm sorry to have caused you the inconvenience.

Thank you for your reply, John!

I have a bit of confusion about your observation of sentence 2.

Do you mean or is used for the purpose of comparison, i.e. the author wants to contrast the number of people living in rural areas with that of city dwellers?

This is the original paragraph:

—————

After millennia of growth so slow that each generation hardly noticed it, the cities are suddenly racing off in every direction. The world population goes up by two per cent a year, city population goes up by four per cent a year, but in big cities the rate may be as much as five and six per cent a year. To give only one example of almost visible acceleration, Athens today grows by three dwellings And 100 square metres of road every hour. There is no reason to believe that this pace will slacken. As technology gradually swallows up all forms of work, industrial and agricultural, the rural areas are going to shrink, just as they have shrunk in Britain, and the vast majority of their people will move into the city. In fact, in Britain now only about four or five per cent of people live in rural areas and depend upon them; [...]

—————

Is it a general preference that or is used to make comparison between ranges of values?

sentence 1 :

you can write "or" here also. It gives a flexible range of 5 or 6 percent.

"five and six percent" also gives a flexible range it means five and six percent is the range it stays within.

Sentence 2:

you need to say "or' because you are doing a comparison of between five or six percent.

sentence 3;

same comments as for sentence one.

so between five and six percent" is grammatically correct, even though it may look incorrect because "and" is usually used to join two clause, but here you are simply joining two percentages together as a range of values.