I read when "be" is used in double comparative, it is sometimes omitted in the book of "Top Notch", like:
The better the quality of health care (is), the higher the life expectancy (is).
According to the above rule, do I have to eliminate both "is" or could I remain either of them?
What if I keep both of them?
In the book of "Top Notch", there are some examples; one of them is like below:
The higher the life expectancy, the larger the elderly population is.
In this example, "is" is used, while the first part does not have a verb. It seems that one of to be verb can be kept while comments below tell me both of them should be eliminated. To this end, I am getting confused which is which.