BACKGROUND AND OBJECTIVE Remarkably little is known about the significance of consensual unions for fertility. This is true everywhere, but the lacuna is more important in the Nordic countries where there is so much childbearing outside of marriage, mostly in consensual unions. The purpose of this paper is to help fill this hole in our knowledge for Finland. DATA Unusually good register data enable us to study recent fertility trends by union status (married, cohabiting, neither) using records for some 112,000 Finnish women, or 11% of all women at fertile ages. METHODS Our description of fertility is based on group-specific duration-based TFRs, which is the number of children borne by a woman who remains in the group throughout her reproductive life, as computed from the fertility rates for a synthetic cohort. This is an intuitively appealing metric that has been taken into systematic use only recently. RESULTS We find substantial fertility differences between women who cohabit, women who marry directly (i.e., without pre-marital cohabitation), and women who marry their cohabitational partner. As one would also expect in Finland, cohabiting women have much lower fertility than married women. The marital TFR is highest among the directly-married and declines monotonically as the length of pre-marital cohabitation increases, even when premarital childbearing is included in the count. As far as we know the latter relationship has not been shown before, because extensive data for complete cohabitational unions have not been available for other populations. CONCLUSIONS The Finnish data are unique, even among the Nordic countries, in that they contain individual-level life histories of family dynamics that cover consensual unions from their very start. Fertility analysis would benefit if data similar to the Finnish were to become available, because analyses that rely on civil status as an indicator of union status barely add anything to what we already know about today's family dynamics.
2013. Vol. 28, 409-419 p.