What are the effects of gentrification in Dennis Lehane's novel Mystic River?

Gentrification occurs when population shifts, upgraded housing, and a surge in investments transform an older, working class neighborhood into a more affluent one, displacing the working class people who live there. The idea of gentrification underlies the story in Mystic River, and was indeed a motivation for Lehane writing the novel. He told Bob Minzesheimer of USA Today that he pondered "what would happen to [a working-class Boston] neighborhood once the Saabs outnumbered the Chevys and the corner store became a Starbucks."

In Boston, this process was accelerated in the late 1990s and early 2000s with a hot real estate market and increasingly high housing costs. Campus housing for the many institutions of higher learning in the city was often in short supply. College students and young urban professionals moved into neighborhoods like the one depicted in Mystic River because housing was cheaper than in other locations. As these new tenants moved into the area, rents increased. The newcomers were willing to pay more than the working-class people that had been living there. This action forced out longtime residents, who had a hard time finding new housing. City officials, including Mayor Thomas M. Menino, and activist groups worked to provide affordable housing solutions for lower income families.