"The Hindu population in East Bengal had declined from 33% in 1901 to 28% in 1941. It fell to 22% by 1951 due to the Partition and the post-Partition exodus, and to 18.5% in 1961. By 1971, it had fallen to 13.5%, partly due to the 1971 massacre by the Pakistani Army, partly due to intermittent waves of emigration. The 1981 figure was 12.1%. In 1989 and 1990, due to "large-scale destruction, desecration and damage inflicted on Hindu temples and religious institutions", "clandestine migration by the Hindus to India went up"."
January 1, 1970
https://en.wikiquote.org/wiki/Demographics_of_India