Resolution criteria

This market will resolve to the United Kingdom's defence spending as a percentage of Gross Domestic Product (GDP) for the year 2027, as published by NATO.

• Primary Source of Truth: The official NATO report "Defence Investment of NATO Countries" (or its direct successor, historically titled "Defence Expenditure of NATO Countries"), which can be accessed on the NATO official website.

• Specific Figure: The resolution value will be the percentage listed for the "United Kingdom" in the table representing "Defence expenditure as a share of Gross Domestic Product" (or the equivalent table representing core defence expenditure as a share of GDP under NATO's updated reporting frameworks).

• Timing: The market will resolve using the 2027 figure published in the 2028 edition of this report (typically released in June or July of 2028), which contains the finalized/revised data for 2027.

• Fallback Rule: If the 2028 report is not published by December 31, 2028, the market will resolve using the estimated 2027 figure ("2027e") published in the 2027 edition of the report. If NATO ceases to publish these statistics, the market will resolve based on official UK government statistics (such as from the Ministry of Defence or the Office for National Statistics) using the NATO-standard definition of defence spending for the 2027–28 financial year.

Background

• In February 2025, UK Prime Minister Sir Keir Starmer committed to increasing the UK's defence spending to 2.5% of GDP by April 2027, using the standard NATO definition.

• Following subsequent NATO commitments to move toward a 5% total defence and security target by 2035 (comprising a minimum 3.5% for core defence), the UK adjusted its trajectory. By mid-2026, UK government plans and independent analyses (such as by the Institute for Fiscal Studies) projected UK defence spending to reach approximately 2.6% to 2.7% of GDP by the 2027–28 financial year.

• NATO's official accounting of defence expenditure includes core military budgets, elements of security and intelligence spending, peacekeeping, and military pensions, which can sometimes differ slightly from domestic UK budget definitions.

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