"1 in 10 are" or "1 in 10 is"?
Take the examples:
- "One in ten children are dyslexic."
"One in ten children is dyslexic."
"One in ten children has dyslexia."
- "One in ten children have dyslexia."
The "one" is singular so 2 and 3 should be correct. But the "one in ten" is a fraction" so 1 and 4 should be correct. And yet I think I usually say 1 and 3. Which is/are correct?!
Solution 1:
Both are commonly used and acceptable.
There are various common cases where a superficially singular subject can or indeed must be associated with a plural verb:
The government [are/is] considering the proposal.
A lot of these matters [have/*has] been dealt with.
The majority [are/??is] pleased with the outcome.
A half of all pensioners [are/??is] living below the poverty line.
In the case you mention, a plural verb is probably at least equally common nowadays as a singular, though historically a singular verb appears to have been more common (e.g. do some comparisons on Google NGram: the singular verb appears to have undergone a downward trend over the last couple of centuries).
You will find prescriptivists bemoaning the apparent contradiction of a singular noun accompanied by a plural verb. But there's really no God-given reason to expect the verb to agree necessarily with the head noun and actual data clearly contradicts this assumption. As is usually the case, the prescriptivists are inventing a problem because their grammatical model is inadequate.
Solution 2:
In data analyzed for the ‘Longman Grammar of Spoken and Written English’ on constructions with one in or one out of followed by a number, plural agreement predominated. ‘The Cambridge Grammar of English Usage’, which quotes this finding, comments that ‘For most writers the choice depends on whether you’re thinking of a single case or a general principle.’
Solution 3:
"One in ten children" may be a fraction, but you are still talking about one child, even as a generality. Out of group of ten children at random, you are considering just one. The singular is/has is appropriate.
If you were to say "10% of children"or "a tenth of all children", then you are talking about a general group of children and the plural are/have is appropriate.