The Word of Until the Next WoUtNW is propinquity.
People of similar demographic attributes tend to live near one another. People are more likely to fall in love with people with similar demographic attributes. People are more likely to fall in love with people they live near.
The tricky question is which way the causality is flowing. Is the tendency towards assortative mating driven by endogamous norms (with or without some innate endogamy drive), or is it just the statistical consequence of assortative residential location plus the tendency people have to fall in love preferentially with people they see fairly often (Russian mail-order brides notwithstanding)?
People of similar demographic attributes tend to live near one another. People are more likely to fall in love with people with similar demographic attributes. People are more likely to fall in love with people they live near.
The tricky question is which way the causality is flowing. Is the tendency towards assortative mating driven by endogamous norms (with or without some innate endogamy drive), or is it just the statistical consequence of assortative residential location plus the tendency people have to fall in love preferentially with people they see fairly often (Russian mail-order brides notwithstanding)?