Secularization, and the decline in religiosity, started around 1880 and first became noticeable after 1960 in the Protestant rural areas of Friesland and Groningen. It later spread to Amsterdam, Rotterdam and the other large cities in the west. In the 1970s, the Catholic southern areas started to show religious declines. The increasing trend towards secularism is countered by a religious revival in the Protestant Bible Belt, and the growth of Muslim and Hindu communities resulting from immigration and high birth rates.