Student or Learner
"rate" is a countable noun.
Therefore, which of the sentences below are correct?
1. The increase in a crime rate is in direct proportion to the number of unemployed.
2. The increase in crime rate is in direct proportion to the number of unemployed.
3. The increase in crime rates are in direct proportion to the number of unemployed.
Thank you very much indeed.
I would say "the increase in the crime rate..." (Or rates, if you had different figures for different categories of crime.)
"Crime rate" doesn't have to be countable. You could consider it an abstract noun. There are a lot of places where an article is not necessary.
"The increase in temperature is due to ... "
"The increase in reading among 5 year olds ..."
"The increase in volume of the dam ..."
But after reading your reply, I think there is an exception to this rule.
Maybe when we emphasize on the type of noun but not its quantity, we can use countable nouns on their own.