Do family, friends or work colleagues influence each other’s fertility decisions? If so, to what extent does this generate a multiplying effect in societies? In a study published in Demography, Zafer Buyukkececi (Humboldt-Universität zu Berlin), Thomas Leopold (University of Amsterdam), Ruben van Gaalen (Statistics Netherlands) and Henriette Engelhardt (University of Bamberg) answered these questions with data from the System of social statistical data sets (SSD), an integrated longitudinal database of various registers and surveys provided by Statistics Netherlands.