I looked up 48201 - which covers most of what we'd call Midtown - in the Census Bureau fact finder, and there was a drop of about 1,000 people from the 2010 population to the 2012 population as estimated by the government's American Community Survey. 48202, which covers the northern tip of Midtown, New Center, and Boston-Edison held steady from 2010-2012. Downtown, 48226, also held steady. [[Technically, both 48202 and 48226 lost population in the 2012 estimate, but we're talking inconsequentially small numbers.)