The 1966 Structural Break: A Formal Test of Change-Point in New Zealand Religious Affiliation Census Data, 1926–2023

New Zealand census data show a well-documented decline in mainline Protestantaffiliation and corresponding rise in non-religious identification from the mid-1960s onward.Despite extensive historical and sociological commentary on this transition, no formalstatistical test of the structural break has been published. We apply the Chow test exhaustivelyacross all candidate break years in the census time series for mainline Protestant share(Anglican + Presbyterian + Methodist), Catholic share, Pentecostal share, and No Religionshare. The optimal break for mainline Protestant decline is identified at 1971 (F = 97.4, p