402 KALMIJN 1967-are a well-known example(Davis 1991).When slavery was abolished, the gradual decline in formal inequality of blacks and whites went hand-in- hand with a growing anxiety about the social boundary between the races,and this anxiety was stronger when contacts were more intimate.Interracial dating and marriage were condemned with great vigor,and strong social norms emerged against interracial contacts with possible sexual undertones,such as interracial dancing and swimming.The emerging doctrine of no social equal- ity was formalized in legislation that segregated the races in public facilities (Jim Crow laws)and legislation that controlled their sexual and marital con- tacts (antimiscegenation laws). Marriage Markets Endogamy and homogamy are not only governed by individual-and group- 'MA wo poppouMo1-6:8661010S level factors,but also by structural arrangements.The chances to marry en- dogamously are higher the more often one meets people within the group and the more often one interacts with group members on a day-to-day basis.Con- tact opportunities are shaped by several structural arrangements.Some studies 多 focus on the demographic composition of the population as a whole,other studies examine regional distributions of groups,and yet other studies analyze smaller,functional settings,such as the school and the workplace. THE LOGIC OF NUMBERS When interaction occurs randomly,the chance that a woman in a certain group marries someone in her own group equals the pro- portion of men who are in that group.As a result,members of a small group will have lower chances of marrying endogamously than members of a larger group.The effect of group size implies that endogamy is negatively related to the degree of heterogeneity of a population(Blau Schwartz 1984).To ex- plain this,one can think of two populations,each consisting of two groups. One population is heterogeneous and has 50%in each group(e.g.100 in group A,100 in group B),while the other is homogeneous and has 90%in one group and 10%in the other (e.g.180 in group A,20 in group B).Both populations 具量 have equal numbers of males and females in each group.In the heterogeneous population,the number of women expected to marry within the group will be 0.5 x 50=25 for A and 0.5 x 50=25 for B,which boils down to 50%marrying within the group.In the homogeneous population,the number of women ex- pected to marry within the group will be 0.9 x 90=81 for A and 0.1 x 10=1 for B,which boils down to 82%.This shows that in a heterogeneous population, endogamy is lower than in a homogeneous population,provided that marriage is random. THE GEOGRAPHY OF GROUPS The chance to encounter a member of one's own group does not depend on group size alone but also on the way a group is1967—are a well-known example (Davis 1991). When slavery was abolished, the gradual decline in formal inequality of blacks and whites went hand-in￾hand with a growing anxiety about the social boundary between the races, and this anxiety was stronger when contacts were more intimate. Interracial dating and marriage were condemned with great vigor, and strong social norms emerged against interracial contacts with possible sexual undertones, such as interracial dancing and swimming. The emerging doctrine of no social equal￾ity was formalized in legislation that segregated the races in public facilities (Jim Crow laws) and legislation that controlled their sexual and marital con￾tacts (antimiscegenation laws). Marriage Markets Endogamy and homogamy are not only governed by individual- and group￾level factors, but also by structural arrangements. The chances to marry en￾dogamously are higher the more often one meets people within the group and the more often one interacts with group members on a day-to-day basis. Con￾tact opportunities are shaped by several structural arrangements. Some studies focus on the demographic composition of the population as a whole, other studies examine regional distributions of groups, and yet other studies analyze smaller, functional settings, such as the school and the workplace. THE LOGIC OF NUMBERS When interaction occurs randomly, the chance that a woman in a certain group marries someone in her own group equals the pro￾portion of men who are in that group. As a result, members of a small group will have lower chances of marrying endogamously than members of a larger group. The effect of group size implies that endogamy is negatively related to the degree of heterogeneity of a population (Blau & Schwartz 1984). To ex￾plain this, one can think of two populations, each consisting of two groups. One population is heterogeneous and has 50% in each group (e.g. 100 in group A, 100 in group B), while the other is homogeneous and has 90% in one group and 10% in the other (e.g. 180 in group A, 20 in group B). Both populations have equal numbers of males and females in each group. In the heterogeneous population, the number of women expected to marry within the group will be 0.5 x 50 = 25 for A and 0.5 x 50 = 25 for B, which boils down to 50% marrying within the group. In the homogeneous population, the number of women ex￾pected to marry within the group will be 0.9 x 90 = 81 for A and 0.1 x 10 = 1 for B, which boils down to 82%. This shows that in a heterogeneous population, endogamy is lower than in a homogeneous population, provided that marriage is random. THE GEOGRAPHY OF GROUPS The chance to encounter a member of one’s own group does not depend on group size alone but also on the way a group is 402 KALMIJN Annu. Rev. Sociol. 1998.24:395-421. 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