Socioeconomic homogamy – choosing a partner from one’s own socioeconomic stratum – is regarded as an indicator of status-group closure in a society. Therefore, changes in socioeconomic homogamy over time are indicative of whether social barriers between status groups are growing or weakening. Various theoretical perspectives suggest that over the course of modernization, group boundaries in terms of socioeconomic family background become easier to cross, whereas homogamy with regard to individually achieved socioeconomic position strengthens. Using Finnish register data and log-linear modelling we analyze changes in homogamy with respect to educational attainment (achieved status) in cohorts born in 1957–79, and in homogamy with respect to social class of the parental family (ascribed status) in cohorts born in 1965–79. We examine the marriages and cohabitations of 30-year-old women in each birth cohort. The results indicate that homogamy in social class origins has weakened only among children of farmers. General educational homogamy shows a small increase from the oldest to the youngest cohort, but the trends differ depending on the level of education: homogamy has strengthened among those with a low level of education, whereas it has weakened among the highly educated. The results further show that women are increasingly inclined to partner with men who are less educated than themselves. The decline in homogamy among the higher educated indicates more social openness in Finnish society, but at the same time the increase in homogamy among those with few educational resources may be a sign of increasing marginalization of this group.