Because seats in the House of Representatives were apportioned on the basis of population, the constitutionally mandated decennial census had important political implications (see Population , ch. 2; The First Republic , ch. 4). The Northern Region's political strength, marshaled by the NPC, had arisen in large measure from the results of the 1952-53 census, which had identified 54 percent of the country's population in that area. A national campaign early in 1962 addressed the significance of the forthcoming census. Politicians stressed the connection between the census and parliamentary representation on the one hand, and the amount of financial support for regional development on the other. The 1962 census was taken by head count, but there was evidence that many enumerators obtained their figures from heads of families, and many persons managed to be counted more than once.

Southern hopes for a favorable reapportionment of legislative seats were buoyed by preliminary results, which gave the south a clear majority. A supplementary count was immediately taken in the Northern Region that turned up an additional 9 million persons reportedly missed in the first count. Charges of falsification were voiced on all sides and led to an agreement among federal and regional governments to nullify the count and to conduct a new census.

The second nationwide census reported a population of 60.5 million, which census officials considered impossibly high. A scaled-down figure of 55.6 million, including 29.8 million in the Northern Region, finally was submitted and adopted by the federal government, leaving legislative apportionment virtually unchanged.

Demographers generally rejected the results of the 1963 census as inflated, arguing that the actual figure was as much as 10 million lower. Controversy over the census remained a lively political issue. NCNC leaders publicly charged the Northern Region's government with fraud, a claim that was denied by Balewa and by Bello, the regional prime minister.

Data as of June 1991