Had you been sitting near me at the paragraph factory yesterday evening, you might have noticed a clenching of the jaw, a narrowing of the eyes, and a pursing of the lips as I came across the construction "7,000 youth."
A quick look this morning at the Corpus of Contemporary American English confirms my suspicion that I have identified another instance of bureaucratic language bleeding into general usage.* The CCAE shows multiple examples of youth in the sense of youths, individual young people, in professional medical and educational publications, fewer frequencies in general publications.
The OED lists a plural sense of youth only when writing or speaking of young people as a group, not as individual units. So say the two most recently published dictionaries I own, the American Heritage and the New Oxford American. So the contagion is not quite general enough for lexicographers to identify it as established. No doubt it's merely a matter of time.
Jargon has its legitimate purposes. Within a profession or specialized group, it's a useful shorthand that permits greater efficiency in communication. It also serves as a marker identifying who belongs in the group and who is an outsider. Journalists who are outside the group adopt its lingo to engage the trust of their sources by showing that they can talk the talk.
Unfortunately, when lay people come across the jargon in a general-interest publication, they clench their jaws, narrow their eyes, and purse their lips.
*The reason this happens, of course, is journalists' regrettable tendency to write for their sources rather than their readers.