May 14 (UPI) -- Population numbers remained about the same in most U.S. midsize cities, the Census Bureau said Thursday. While the national population grew slowly, the population in major cities dropped, a new report from the Census Bureau said. The Bureau defines midsize cities as those with populations of 25,000 to 70,000. An example is Fort Mill, S.C., which was the fastest-growing city in the Charlotte, N.C., metro area. Its population increased by 6.8%, to 38,673. Its growth was faster