The National Bureau of Statistics is preparing to “normalise” Nigeria’s December 2025 inflation figures to prevent what it describes as an artificial spike in the Consumer Price Index, CPI, that could mislead policymakers, investors and the public.
The move follows the recent rebasing of the country’s inflation series, a major statistical overhaul that has shifted the CPI base year from 2009 to 2024. While the exercise is intended to better reflect current consumption patterns and price realities, it has also created powerful base effects that are expected to distort the headline inflation rate for December.
Senior officials of the Bureau disclosed the plan during a virtual stakeholders’ engagement convened jointly with the Nigerian Economic Summit Group, NESG. The session brought together statisticians, economists, regulators and private-sector analysts to examine the implications of the rebasing and the appropriate treatment of the December data.
Analysts had already warned that the December 2025 inflation print could jump sharply on paper, with projections in the 31.4 to 32.4 per cent year-on-year range, even if underlying price pressures did not worsen materially. The NBS now confirms that this spike would be largely technical, not economic.
Statistician General of the Federation and Chief Executive Officer of NBS, Adeyemi Adeniran, explained that the projected surge is a direct consequence of the methodology used to link the old CPI series to the new one, rather than a reflection of fresh inflationary shocks.
He said the rebasing exercise, which adopts 2024 as the new base year after a 15-year gap, required that December 2024 be set equal to 100 in the new index. That decision, while statistically convenient, created a narrow and unusually sensitive reference point for calculating year-on-year inflation in December 2025.
“Following the rebasing exercise and the methodology adopted for December 2025, a significant artificial spike in the inflation rate is expected,” Adeniran told participants. “This spike arises from the base effect, with December 2024 equated to 100 following the rebasing.”
He stressed that base effects are a normal feature of index-based statistics worldwide, especially when comparing periods with unusually high or low prices. However, he warned that when such effects are purely arithmetic and not rooted in structural changes in the economy, they must be clearly explained and, where appropriate, adjusted for.
“Transparency requires that we provide a clear picture of actual price changes rather than simply reporting an artificial spike that does not reflect economic realities,” he said, adding that the Bureau’s decision to address the issue proactively was guided by accountability and the need to preserve confidence in official data.
In his remarks, NESG Chief Executive Officer, Dr Tayo Aduloju, framed the debate within Nigeria’s broader macroeconomic transition. He argued that as the country moves from emergency stabilisation measures to a phase of consolidation and growth, the quality and interpretation of inflation statistics become even more critical.
“As the economy shifts from stabilisation reforms to consolidation reforms, the role of official statistics, especially the CPI, becomes very crucial,” Aduloju said. He noted that in times of acute instability, headline inflation serves as an alarm bell, but in a consolidation phase, it must help policymakers and markets understand inflation dynamics rather than simply react to headline numbers.
Aduloju cautioned that misreading a technically inflated CPI figure could trigger policy errors with far-reaching consequences. “In this phase of macroeconomic transition, policy errors can be very costly,” he said. “Credible CPI statistics anchor policy coherence, guide monetary policy calibration, inform fiscal planning, shape wage negotiations, and influence investment decisions.”
Providing the technical backbone of the discussion, Director of Price Statistics at NBS, Dr Ayo Anthony, walked stakeholders through the methodological challenges created by the rebasing and the solution the Bureau intends to apply.
Anthony recalled that the last CPI rebasing was conducted in 2009, even though international best practice recommends such exercises roughly every five years. The long delay meant that Nigeria’s official inflation basket had become increasingly detached from actual consumption patterns.
“Because of this 15-year gap, consumption patterns changed significantly,” he said. “We introduced over 400 new products into the CPI basket and removed more than 200 items.” The new CPI now covers 934 products and is structured around a 13-division COICOP classification, aligning more closely with global standards.
However, linking this rebased series to the old one in order to compute year-on-year inflation created what Anthony described as “unavoidable statistical complications.” Using December 2024 as the single reference month with an index value of 100 allowed the two series to be bridged, but it also amplified base effects for December 2025.
“Projections show that without adjustment, December year-on-year inflation could appear excessively high due solely to arithmetic base effects, rather than underlying economic conditions,” he said.
