Repeated Seasonal Swings in UK GDP Data Prompt Fresh Scrutiny From Economists

A recurring seasonal pattern in Britain’s economic growth figures has raised new questions among economists about the reliability of official data, after quarterly numbers again showed stronger performance in the first half of the year and weaker results toward the end.

Data released on Thursday indicated that the UK economy grew fastest in the first quarter of 2025, recorded solid expansion in the second quarter and then slowed noticeably in the third and fourth quarters. Growth in the final three months of 2025 was just 0.1 percent, compared with 0.7 percent in the first quarter. The same pattern has appeared each year since 2022.

While a single year of uneven growth might be explained by specific economic shocks, the repeated nature of the trend has fuelled concerns that seasonal adjustments may not be fully capturing underlying changes in the economy since the pandemic. Seasonal adjustment is a standard statistical process used by national agencies to smooth out predictable fluctuations such as Christmas spending, summer tourism or winter energy demand.

The Office for National Statistics has previously faced criticism over data quality, particularly in labour market surveys affected by lower response rates. However, gross domestic product figures have not been subject to the same level of scrutiny until recently. Some economists now believe the pattern in quarterly GDP may suggest that the adjustment methods are struggling to reflect post pandemic shifts in consumer and business behaviour.

Matt Swannell, chief economic adviser at EY ITEM Club, said the consistency of stronger first and second quarter growth compared with the latter half of the year makes it more difficult for policymakers to assess the true direction of the economy. He argued that the distorted pattern increases uncertainty about the outlook and complicates decisions by the Bank of England, particularly when considering potential interest rate changes.

The ONS said it had examined the issue and published a report last year which found no evidence of problems when looking at a longer historical data series. A spokesperson said there was no cause for concern and that methods remain under close review. The agency pointed to several one off events in recent years that could have contributed to the pattern, including a surge in exports to the United States ahead of expected tariffs and uncertainty surrounding domestic tax policy.

Other analysts have suggested that persistent inflation since 2022 may also play a role. James Smith, a developed markets economist at ING, said price increases may have been more heavily concentrated in the first half of the year, potentially affecting how seasonal adjustments interpret economic activity. He noted that pinpointing the exact cause is difficult, but acknowledged that something in the data may not be fully aligning with broader economic trends.

Despite the debate, some forecasters expect the familiar rebound to appear again in the first quarter of this year. If that happens, attention is likely to intensify over whether the pattern reflects genuine economic behaviour or technical challenges in the way Britain’s growth data is processed.