National survey on social cohesion and modernization in the Netherlands.This survey builds on earlier waves of the Religion in Dutch society survey, which have been conducted in the winters of 1979/1980, 1985/1986, 1990/1991, 1995/1996, 2000/2001, 2005/2006, 2011/2012, and the Social and Cultural Developments in the Netherlands survey 2017, 2018 and 2019.They are part of a long-standing research program, aimed at longitudinal research with a strong (a) substantial multi-disciplinary focus on religiosity, values, in-group solidarity and out-group derogation as well as a strong (b) methodological focus on high quality data, valid measurements and innovative data-collection designs.The most recent data collection for 2020 improves possibilities to test hypotheses on processes of secularization and individualization, spanning a period of more than forty years.DANS Data Guide 20 available (open access); dataset SOCON 2020 available as of January 2023 (restricted access).