http://www.usatoday.com/story/news/2015/03/02/urban-donut-demographics-poverty/24281675/
This is not an issue that Nashville faces alone, per the USA today article,
"For most cities, the downtown was the poorest, least educated place" a generation or two ago, said Luke Juday, a research and policy analyst at U.Va.'s Weldon Cooper Center Demographics Research Group. Since 1990, urban downtowns and central neighborhoods have attracted "significantly more" young, educated, high-income residents. The developments are happening for several reasons, said Juday, including policy shifts that moved public housing away from concentrated high-rises in city centers. Long-term trends such as lower urban crime rates and a rise in demand by Millennials for "walkable neighborhoods" have also had an effect.