  We study the structure of heterosexual dating markets in the United States
through an analysis of the interactions of several million users of a large
online dating web site, applying recently developed network analysis methods to
the pattern of messages exchanged among users. Our analysis shows that the
strongest driver of romantic interaction at the national level is simple
geographic proximity, but at the local level other demographic factors come
into play. We find that dating markets in each city are partitioned into
submarkets along lines of age and ethnicity. Sex ratio varies widely between
submarkets, with younger submarkets having more men and fewer women than older
ones. There is also a noticeable tendency for minorities, especially women, to
be younger than the average in older submarkets, and our analysis reveals how
this kind of racial stratification arises through the messaging decisions of
both men and women. Our study illustrates how network techniques applied to
online interactions can reveal the aggregate effects of individual behavior on
social structure.
