The Netherlands and its secularisation

According to Statistics Netherlands, 2017 is the first year a majority of the Dutch population (51%) have stated they do not belong to any religious group. For comparison, in 1971, 23% of the Dutch population was non-affiliated. In 2017, almost 25% of the Dutch was affiliated to the Roman Catholic Church, 15% to a protestant church and 5% was Muslim.
Next to affiliation, one could derive the Dutch process of secularisation from attendance at religious services: in 1971, 37% of the Dutch population attended religious services on a regular basis - at least once per month - but this share had dropped to 16% in 2017.

Source: Statistic Netherlands (2018): Over half of the Dutch population are not religious.