The NBS will normalise December 2025 inflation data, correcting base effects from CPI rebasing for accurate economic reporting

The National Bureau of Statistics (NBS) has announced plans to normalise Nigeria’s inflation data for December 2025 following a projected spike in the Consumer Price Index (CPI), which the Bureau attributed to statistical base effects rather than underlying economic conditions.

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The clarification came during a virtual engagement on Monday convened by the NBS and the Nigerian Economic Summit Group (NESG).

Statistician General of the Federation and NBS CEO, Adeyemi Adeniran, explained that the spike stems from the rebasing of the CPI to 2024 as the new base year, marking the first rebasing since 2009.

“Base effects are common in statistical practice, particularly when comparing data across periods with unusually high or low prices. The expected spike in December 2025 arises from this arithmetic effect and is not reflective of structural economic changes,” Adeniran said.

The NBS will apply a normalisation process, using the average CPI from January to December 2024 as the reference period, instead of equating December 2024 to 100.

This adjustment, in line with the CPI Manual 2020, aims to remove artificial distortions and provide a clearer picture of inflation trends.

Dr Ayo Anthony, Director of Price Statistics at NBS, outlined methodological changes resulting from the rebasing, which introduced over 400 new products into the CPI basket and removed more than 200 items, reflecting evolving consumption patterns.

Anthony noted that without adjustment, December 2025 inflation could appear artificially high.

NESG CEO Dr Tayo Aduloju emphasised the importance of credible CPI data for policy formulation, stating that misleading inflation signals could undermine macroeconomic stability as Nigeria transitions from stabilisation to consolidation reforms.

While the normalisation affects published figures from January to December 2025, the NBS assured stakeholders that the impact is minor and will be clearly communicated.

From January 2026 onwards, the base effect will no longer influence CPI calculations, as comparisons will rely solely on actual rebased index values.

However, some economists expressed concerns over credibility.

Former Zenith Bank chief economist Marcel Okeke warned that adjusting figures could undermine confidence and comparability with other economies.

Investment banker Adetilewa Adebajo

echoed these concerns, questioning how inflation could appear to double from November to December without reflecting real price changes.

The NBS affirmed that the normalisation follows global best practices, with consultations from the IMF, World Bank, and Central Bank of Nigeria.

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Adeniran stressed the importance of regular rebasing to avoid distortions and improve the accuracy of economic indicators.