A country's economy is not measured. It is estimated, using a formula, and the formula has a base year baked into it.
Nigeria's base year was 2010, and by 2014 it had gone badly out of date. The formula was still weighting the economy as though telecoms, film production, online sales, airlines and music barely existed. So Nigeria rebased, shifting the calculation onto more current foundations.
The economy went from roughly $270 billion to about $510 billion. A rise of nearly 90%, in a single announcement. Nigeria passed South Africa, then on about $370 billion, and became the largest economy on the continent.
Not one additional item was manufactured. The country woke up the same size it had been the night before. What changed was the counting.
For comparison:
- The 2014 rebasing added roughly $240 billion of measured economy overnight
- By 2024, currency devaluation had pushed Nigeria down to 4th in nominal terms
- A second rebasing in 2025 lifted nominal GDP by another 34% and moved the ranking not at all
- Measured by purchasing power rather than exchange rates, Nigeria sits 2nd, more than double South Africa
That last line is the one worth holding onto. Ask which country has Africa's largest economy and you get a different answer depending on whether you use market exchange rates or purchasing power, which year's projections you read, and how recently the statistics office updated its formula. All three answers are defensible. None of them is wrong.
The 2025 rebasing has now put Nigeria on a five-year cycle, which is what the international standard recommends. Fewer decades of drift, fewer overnight leaps.
An economy is a thing you can walk around in. Its size is a thing somebody decided how to measure.