In An Appraisal of the Iglesia ni Cristo, author Albert J.
"Although Eraño Manalo declared in 1963 that the membership
of the Iglesia was 3,500,000, many informed observers dispute this
claim and regard this figure as grossly inflated. The 1960 census registered
270,104 members of the Iglesia. The members are concentrated in the
greater Manila area, especially in the Rizal province."
"By 1968 membership was estimated at 500,000. From the figures of
the 1970 census, INK membership in the Philippines is around 475,407."