Because the title uses the word "several". Had it been replaced with "a few", the reaction would be consistent with what the reader would feel after reading the full article, and the statistics.

original > Young women earn more than young men in several U.S. cities

vs.

alt. 1 > Young women earn more than young men in a few U.S. cities

or

alt. 2 > Young women earn more than young men in some U.S. cities