We have to consider what we are saying in this sentence. We are considering that there are many homeless people. The construction of the sentence says that one in five is. Grammatically, we want to say that this is a correct construction. Actually, we are considering a number of people who are homeless.
If you were to say "One out of those five people over there is homeless," you are speaking of only one person, not of a collective group.
Look at this example: Many homeless animals are euthanized daily, at least one in five.
One in five animals are euthenized daily.
Because we are considering a larger number than one, our minds and our ears want to say, "One in five are homeless..."
It sounds awful to my ear to say, "One in five is homeless".
This is only my opinion and rationale. I would have to look up a rule and I don't know if it exists.
For most of us, it's "One in five homeless people are employed" but "One homeless person in five is employed". "One in five" refers to a fraction of the total, but "one person" is a person.Is it one in five homeless people ARE in employed or
one in five homeless people IS employed?
Yes, and "A ton of coal was all being dumped in the boat at once."In the above example, "a ton of" is not meant as a concrete weight, it means "a great many" and it therefore takes a plural verb.
We would say "A ton of coal is too much for the boat to carry" because we mean "a ton" and not "a great many".