Table 1.

Indices of Ethnic Density and Segregation

Ethnic density measure	Common areas of measurement	Description	Studies
MEASURES OF ETHNIC COMPOSITION
% Black or Hispanic/Latino or Mexican American; % Franco ancestry	Census block group, tract County	Often divided into quartiles or other categories	8, 9, 13, 19, 26, 29, 30, 32, 38, 40, 42–44, 47–49, 53
% recent immigrants or % foreign-born	Census block-group, tract	‘Recency’ not always defined, but sometimes defined as within last 5 years	41, 42, 45, 58
Language	Census tract	Often conceptualized using any or a combination of the following items: -% speaking Spanish/Asian language -% linguistically isolated (% households lacking at least one member who speaks English ‘well’ or ‘very well’ -% limited English proficiency (Definitions varied: Generally included individuals who reported speaking English ‘Not at all’ or ‘Not well’ but could also include individuals who reported speaking English ‘well,’ excluding only those speaking English ‘very well’) -% children speaking Yiddish at home (<5%, 5–20%, >20%)	28,41, 42
Immigrant concentration	Census tract	Often conceptualized using a combination of the following items: -% Hispanic -% foreign-born -% limited English proficiency -% linguistically isolated -Isolation Index (see measures of residential segregation below)	16, 39
Enclave index	Census tract	Neighborhood Hispanic or Asian enclave index based on: -% linguistically isolated -% linguistically isolated who speak Spanish/Asian language -% speaking limited English -% speaking limited English who spoke Spanish/Asian language -% of recent immigrants -% Hispanic/Asian -% foreign-born Derived using principal components analysis across block groups, with block group values averaged across census tracts. In some studies, quintiles dichotomized to lower (quintiles 1–3) or higher (quintiles 4 and 5) enclave status	14, 15, 18, 20–25, 27, 54–57
MEASURES OF RESIDENTIAL SEGREGATION
EVENNESS: Spatial distribution of the subject population
Dissimilarity Index	Census tract	The degree to which each neighborhood has the same distribution of the subject population compared to the majority population as the larger region (e.g., metropolitan area or county) overall; the proportion of persons of the subject population in a neighborhood that would have to move for the neighborhood to have the same racial distribution as the surrounding, larger region.	8, 9, 16, 42, 51
Multigroup Dissimilarity Index	Census tract	A version of the dissimilarity index generalized to capture concurrent segregation between multiple racial/ethnic groups.	31
Theil index	Metropolitan area	Represents proportion of subject population that would need to move to a different neighborhood to achieve an even distribution within the region.	48
EXPOSURE: Degree of potential contact, or possibility of interaction, between minority and majority group members
Isolation Index	Census tract Other area (county, state)	The extent to which members of the subject population are exposed to other members of their own group (as opposed to members of the majority population) in their neighborhood. May be calculated using either a place-centered or person-centered approach.	8, 9, 16, 33–37, 46, 50, 52
CONCENTRATION: Relative amount of physical space occupied by a minority group in the region
Delta	Census tract	The relative (to population size) amount of physical space occupied by the subject population in a given neighborhood; situations in which the subject population is of the same relative size as the majority population but occupies less space would indicate greater concentration (and hence greater residential segregation)	8, 9
CENTRALIZATION: Degree to which a group is spatially located near the center of an urban area
Relative centralization		The extent (relative to the majority population) to which members of the subject population are located near the center of the metropolitan area; a dimension of residential segregation in the US because of historical circumstances that ‘confine[d] minorities to declining central city areas’	8, 9
CLUSTERING: Extent to which areal units inhabited by minority members adjoin one another, or cluster, in space
Spatial Proximity	Census tract	The extent to which neighborhoods of the subject population are adjacent to each other in physical space, relative to the majority population; a high degree of clustering is generally interpreted as representing a ghetto or ethnic enclave.	8, 9
LOCAL SEGREGATION INDICES
Location quotient (LQ)	Census tract	The ratio of the proportion of the subject population in the neighborhood divided by the proportion of the subject population group in the larger surrounding region; represents the concentration or density of a population group in an area relative to the larger region	10–12
Local Exposure/Isolation (Lex/Is)	ZIP Code Tabulation Areas (ZCTAs)	The probability that two individuals (of either the same or different race/ethnicity) living within a specific areal subunit will interact. A zero value indicates that the estimated probability of interaction in the subunit is equivalent to the probability in the larger metropolitan statistical area (MSA). Values > 0 indicate that interaction is more likely to occur in the subunit than in the MSA, whereas values < 0 indicate that interaction is less likely.	11
Index of concentration at extremes (ICE)	ZIP Code Tabulation Areas (ZCTAs) County	This index characterizes the extent to which an area’s population is concentrated in extreme deprivation or extreme privilege. The index ranges from −1 to 1. A value of −1 indicates that 100% of the population is concentrated in the most deprived group, whereas a value of 1 indicates that 100% of the population is concentrated in the most privileged group.	11