“…However, most commonly they have been measured in terms of census tracts with a relatively high ethnic-group percentage, either as a value applied consistently to the various groups or as a variable percentage or location quotient based on the group's percentage in the city or metropolitan area as a whole (Hum and Zonta, 2000;Logan et al, 2002;Poulsen et al, 2002;Pamuk, 2004). Several scholars have defined ethnic concentrations as those census tracts in which the group's proportion was five times that in the metropolitan area as a whole (Logan et al, 2002;Parks, 2004;Allen and Turner, 2005). However, in places where ethnic groups constitute only a very small proportion of the total population, much lower thresholds seemed more appropriate to some scholars- Chung and Brown (2007) considered an ethnic concentration in Columbus, Ohio, to be those tracts in which the group's percentage was at least 1.33 times that in the metropolitan area as a whole.…”