After two decades of very high growth, Nagaland's population declined between 2001 and 2011 though there were no epidemical diseases, wars, famines, natural calamities, political disturbances, or any significant changes in the state's socio-economic characteristics. This decline is unprecedented in the history of independent India. It has been shown that the census estimates of the state's population for 1981-2001 are internally inconsistent. In the light of this, this paper uses information from the Sample Registration System and National Family Health Surveys to examine the reliability of the census figures in Nagaland between 1971 and 2011. It suggests that the census estimates are inconsistent with these sources of information.