The National Bureau of Statistics (NBS) has announced plans to normalise Nigeria’s inflation figures for December 2025 following projections of a sharp spike in the Consumer Price Index (CPI), which it says is driven largely by technical base effects rather than underlying economic conditions.
The disclosure was made on Monday during a virtual stakeholders’ engagement jointly convened by the NBS and the Nigerian Economic Summit Group (NESG).
According to the Bureau, the anticipated rise in December inflation is linked to the recent rebasing of the CPI series, not to any sudden deterioration in economic fundamentals. Analysts have projected headline inflation for December to rise to between 31.4 per cent and 32.4 per cent year-on-year, largely on account of base effects.
Providing the official position of the Bureau, the Statistician-General of the Federation and Chief Executive Officer of the NBS, Mr Adeyemi Adeniran, explained that the projected spike stems from the rebasing of the CPI, which adopted 2024 as the new base year after a 15-year interval from the previous 2009 base year.
He noted that base effects are a common feature of index-based statistical measurements, particularly following rebasing exercises.
“Following the rebasing exercise and the methodology adopted for December 2025, a significant artificial spike in the inflation rate is expected, as some analysts have already projected. This spike arises from the base effect, with December 2024 equated to 100 after the rebasing,” Adeniran said.
“Base effects are neither unexpected nor unusual in statistical practice. However, when they are artificial and arithmetic rather than reflective of structural changes in the economy, it is essential to clearly explain them to data users.”
Adeniran said the decision to proactively address the issue was guided by the principles of transparency and accountability.
“Transparency requires that we present a clear picture of actual price movements rather than simply reporting an artificial spike that does not reflect economic realities. This engagement is to properly inform our stakeholders and users of our data,” he added.
In his opening remarks, NESG Chief Executive Officer, Dr Tayo Aduloju, stressed the growing importance of credible inflation data as Nigeria transitions from economic stabilisation to consolidation.
“As the economy moves from stabilisation reforms to consolidation reforms, the role of official statistics—especially the CPI—becomes even more critical,” Aduloju said.
He noted that preliminary assessments suggest inflation figures could experience temporary technical spikes, cautioning that such outcomes should be carefully interpreted.
“During periods of acute instability, headline inflation serves as an alarm bell. But as we shift from managing crisis to managing growth, CPI statistics must help us properly understand inflation dynamics, not just react to headlines,” he said.
Aduloju warned that misleading inflation signals at this stage of macroeconomic transition could undermine policy gains, noting that “policy errors can be very costly” during consolidation. He added that credible CPI data remain central to policy coherence, monetary policy calibration, fiscal planning, wage negotiations and investment decisions.
Delivering the technical presentation, Director of Price Statistics at the NBS, Dr Ayo Anthony, outlined the methodological challenges created by the rebasing exercise and the measures taken to address them.
“The last CPI rebasing was done in 2009, whereas global best practice recommends rebasing every five years,” Anthony said. “Over the 15-year gap, consumption patterns changed significantly, resulting in the introduction of over 400 new products into the CPI basket and the removal of more than 200 items.”
He explained that linking the new CPI series—comprising 934 products under a 13-division COICOP classification—to the old series created unavoidable statistical complications.
“To compute year-on-year inflation, the rebased CPI had to be linked to the old series. Setting December 2024 equal to 100 enabled this linkage but also introduced the base effect now being observed,” he said.
Anthony warned that without adjustment, December 2025 inflation could appear significantly inflated due solely to arithmetic effects.
To address this, he said the NBS would apply a normalisation process in line with the CPI Manual 2020 (Chapter 9, Section 9.125), which allows for the maximisation of the index reference period. Under this approach, instead of using a single-month reference period, the average CPI from January to December 2024 will be set equal to 100.
“This adjustment removes the artificial base effect and presents a more accurate picture of inflation dynamics,” Anthony said, adding that while the adjustment affects published figures for January to December 2025, the impact is minimal and will be clearly communicated.
“We are not hiding anything. For transparency, we will still reference the artificial spike in our reports,” he said.
Anthony also disclosed that the decision followed consultations with key technical partners, including the International Monetary Fund, the World Bank and the Central Bank of Nigeria.
Looking ahead, he noted that the base effect would no longer apply from January 2026, as inflation calculations would be based entirely on the rebased CPI basket.
“From January 2026 onward, comparisons will rely on actual index values from the rebased basket,” he said.
The NBS used the engagement to reiterate the importance of regular rebasing of macroeconomic indicators, stressing that timely rebasing of CPI and GDP would help prevent similar distortions in the future.
The Bureau reaffirmed its commitment to sustained stakeholder engagement, methodological rigour and clear communication as part of efforts to strengthen confidence in Nigeria’s official statistics.
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