From the Oxford Advanced Learner's Dictionary:
Small shops have been a casualty of the recession.
"Shops" is plural here while "casualty" is singular. Any reason for that?
Can I have the sentence stick to one form?
Small shop has been a casualty of the recession.
Small shops have been casualties of the recession.
Thanks in advance.
The reason for the use of the singular casualty is to imply that small shops (collectively) are one casualty among many other groups of entities. Another example:
Private equity funds are a significant factor in the rapid increase in housing prices, in certain markets.
It may be grammatical to say "the funds are significant factors", but this changes the meaning to suggest that the funds each have a separate effect, rather than that, together, they have a collective effect among other (unmentioned) groups that also have an effect (e.g. foreign investors, families with rising incomes, etc.)
Of course if we were talking about one specific fund, then we would use the singular:
The Donald Trump 'Best Fund in the World' Fund is a significant factor in ...
The first sentence is grammatically correct, as small shops is talking about the singular collection of small shops, not any small shop in particular.
In other words, Small shops is one noun referencing one collection, so it is singular.
As Andrew pointed out, there is an important distinction between the two sentences that I forget to address. When someone says Small shops have been casualties of the recession, you are saying that many individual shops have caused separate casualties rather than small shops as a whole. Both are valid, but the Small shops have been a casualty of the recession makes more sense
When you refer to a group of things and the nature of the group is more important than the identity of the individual members, you will likely use a collective noun.
Some collective nouns are distinct from their individual forms, e.g., "The herd fled when a lioness approached." Herd is the collective noun, and the individual members might be gazelles or antelopes.
Other nouns, such as "shops" do not have different words for plural vs collective usage. In this case, the collective usage is determined by the grammar of the sentence.
The use of "small shops" as a collective noun indicates (1) that all small shops were hurt by the recession in some manner, and (2) that being a member of the "small shops" class is sufficient to receive that harm.
