The United Nations has approved changes to include wind, waves, and data in the calculations of countries' economies for the first time. This update aims to capture the value of natural resources and data, reflecting their growing importance since the last update in 2008.

Starting in 2030, these changes could increase estimates of the UK economy's size, making promises to spend a fixed share of the economy on defense or aid more expensive. The economic value of wind and waves will be estimated based on the energy generated from turbines, while data will be treated as an asset alongside servers and cables.

Governments use a common rule book for measuring economic size and growth. These changes are considered "tweaks" rather than a complete rewrite, according to Prof Diane Coyle of the University of Cambridge. Ben Zaranko of the Institute for Fiscal Studies (IFS) calls it an "accounting" change, noting that it won't materially improve wealth or tax revenues but could make economies appear larger.

For example, Labour's commitment to allocate fixed percentages of the economy to defense and aid could see an increase in defense spending by £2bn if the new rules boost the economy's size by 2-3% in 2030. This could create future spending challenges for the UK government.

The Office for Budget Responsibility (OBR) will not include the impact of these new rules in their March assessment of government finances, making it a future concern for the Chancellor.