I’ve just looked it up and it’s called seasonal adjustment.
GDP naturally has seasonal patterns. Christmas, for example, causes retail activity to surge in December and then fall back in January. The ONS therefore adjusts the raw figures to remove predictable seasonal effects, so that Q1 can be compared fairly with Q4. That’s standard statistical practice.
Interestingly, the ONS has actually acknowledged a genuine issue that’s relevant to what you’ve heard. It says that UK economic activity has developed a stronger pattern of growth at the start of the year in recent years, and that seasonal adjustment has had to adapt to this changing pattern. It says it can take 3–5 years of data to establish a new seasonal pattern properly.
And historically, Q1 certainly hasn’t always shown growth. The ONS says that before the pandemic, raw (unadjusted) GDP typically fell sharply in Q1; in the two pre-pandemic years it averaged −3.4% in Q1. After seasonal adjustment, however, Q1 growth averaged +0.3% in that earlier period.
What’s particularly interesting about 2026
The ONS’s current figures show:
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Q4 2025: +0.2%
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Q1 2026: +0.6%
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Q2 2026: +0.4%
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So it’s not simply a case of
“Q1 always grows because of the way they adjust Christmas.” Q2 has also subsequently grown.
However, there is a legitimate debate about the reliability of the recent Q1 numbers, because the seasonal pattern of the UK economy has changed and the ONS itself says the models are having to adapt to that. The ONS is specifically monitoring this and says its latest statistical tests found no statistically significant residual seasonality in the aggregate GDP figures.
This is also an interesting point;
GDP per head tells a less impressive story for Britain
The same ONS/OECD comparison has UK GDP per head growing 1.1% in 2025, compared with 0.7% in Italy.
So Britain still comes out ahead, but by much less. And UK GDP per head actually fell in Q4.
That’s because Britain’s population has been growing relatively rapidly. Total GDP can increase while the improvement experienced by the average person is considerably smaller.
So the rapidly growing population has an impact with those figures.
The UK’s total GDP growth has been better, but there are serious weaknesses underneath it — particularly productivity, GDP per capita, business investment, government debt/finances and the labour market.