The decline of fertility in the course of the Second Demographic Transition is mainly caused by both an increase in childlessness and a decline of large families (three or more births). Which of these effects are stronger in Germany has been contested for a long time. An exact quantification of the particular effects is still missing. In this paper we develop a decomposition method which allows calculating the effects of the particular parity changes between cohort total fertility rates (CTFR) of different cohorts. This method is applied in order to compare German CTFRs for the cohorts the fertility decline occurred in, namely the cohorts between 1933 and 1968. The analyses are differentiated by regions and periods. The CTFR decline can be separated into four components: increasing childlessness, decreasing shares of higher order births (3+), a combined effect and a changing relation of first and second births. In Germany, the effect of the increasing childlessness accounts for 25.9 per cent of the CTFR decline, the decreasing higher order births for 68.0 per cent and the combined effect for 6.1 per cent. The relation of first and second births changed only marginally. Remarkably, these figures are based on two entirely different periods: The CTFR decline between the cohorts of 1933 and 1947 is solely based on the decline of women with three or more children. However, two thirds of the CTFR decline since 1947 is caused by an increasing childlessness. The results are relevant for fertility theories because increasing childlessness and decreasing higher order births have different reasons.