The benefi ts of urban agglomeration cannot take place if city living
exposes the population to deadly levels of ambient air pollution and raises
the risk of experiencing infectious diseases such as cholera, diarrhea, and
dysentery (Melosi 2000). At the turn of the twentieth century, the average
white urbanite in the United States paid a ten- year “mortality penalty” for
not living in the countryside (Haines 2001). By 1940, big- city investments
in water treatment and sanitation signifi cantly reduced the threat of water
pollution (Cutler and Miller 2004; Haines 2001).
Over the twentieth century, U.S. big cities have experienced rising and
then declining levels of crime and pollution. Ambient air pollution grew
sharply over the twentieth century, peaking in the early 1970s and declining
over the last thirty years. Urban crime rates have been documented to have
risen during the 1970s and 1980s and to have declined sharply since the early
1990s (Levitt 2004; Reyes 2007).
At this point in time, big cities feature more congestion, pollution, and
crime than smaller cities (Glaeser 1998; Glaeser and Sacerdote 1999). These
nonmarket local public bads can signifi cantly reduce big- city quality of life
(Tolley 1974; Blomquist, Berger, and Hoehn 1988; Gyourko and Tracy
1991). In contrast, larger cities offer greater cultural amenities and a better
variety of shopping and cuisine options than smaller cities (Waldfogel 2008).