In 2024 the National Bureau of Statistics rebased Nigeria’s Consumer Price Index, moving the base year from 2009=100 to 2024=100. A rebasing is routine statistical hygiene — it refreshes the consumption basket and the expenditure weights to reflect how households actually spend today, and re-anchors the index level to a recent year. But it also creates a discontinuity, and that discontinuity is being read wrong across a lot of Nigeria commentary.
What actually changed
Three things moved at once in the 2024 rebase: the base period (to 2024=100), the item basket (updated to a more recent picture of household consumption), and the weights attached to each category. Because all three changed together, a year-on-year rate computed on the new series is not measuring the same object as one computed on the old series. They share a name — “headline inflation, % year-on-year” — and almost nothing else.
The mistake, concretely
On the old (2009=100) series, headline inflation peaked around 34.8% in 2024. On the rebased (2024=100) series, the current read is 15.93% (May 2026). It is tempting to subtract one from the other and narrate a collapse in prices of nearly twenty points. That subtraction is meaningless: a large part of the step down is the base-and-basket change, not month-over-month disinflation. The prices Nigerians pay did not fall by the arithmetic difference between two indices built on different foundations.
There is real disinflation in the data — the rebased series itself has fallen materially over 2025–2026 as the naira found a floor and base effects washed through. But you can only see it, and size it correctly, by staying inside one series.
The rule
Compare rebased figures to rebased figures. Any year-on-year comparison that mixes a pre-rebase print with a post-rebase print is methodologically unsound, and any chart that splices the two series into one continuous line is drawing a discontinuity as if it were a trend. Several Nigerian data aggregators still publish the old series alongside the new without flagging the break — which is how the false comparison keeps circulating.
What ONYX does
ONYX carries the rebased CPI (2024=100) from 1995 onwards, back-converted from NBS publications so the whole history sits on one consistent basis. When a source disagrees — and for this series several do — we retain the alternate as a superseded, dated record rather than deleting it. The canonical value we serve is the NBS primary, rebased, with the period clearly marked, so a year-on-year figure you pull is always comparing like with like.
Why the correct number matters for a decision
This is not pedantry. At an MPR of 26.5% and headline inflation of 15.93%, Nigeria’s real policy rate is approximately +10.6% — unusually high, and the single biggest reason portfolio capital has flowed in. Get the inflation basis wrong and you misprice the real rate, misread the CBN’s room to cut, and mis-time the call that follows. A defensible macro view starts with an inflation number you can actually stand behind.
Every figure here shows its receipts
The rebased CPI series, its superseded alternates, and the source and period behind every print live in the ONYX platform. To request the Terminal, or a reconciled Nigeria macro data feed for research or investment committee use: hello@onyxdata.io.