Evaluation of the ONS’ ARIES programme

About the study

The Office for National Statistics (ONS) launched the Ambitious Radical Inclusive Economic Statistics (ARIES) programme in April 2021 to sustainably improve the quality, timeliness and granularity of the ONS economic statistics through best use of available data and technology. This initiative built upon the preceding Economic Statistics Transformation Programme (ESTP) but was specifically designed to address an evolving and increasingly complex set of user demands and operational challenges.

In 2024, the ONS commissioned NatCen to undertake an evaluation of the ARIES programme. The evaluation aimed to assess the implementation and impact of the ARIES programme and is focused on six ARIES projects: Prices, Public Sector Finance Statistics, Labour Market, Legacy Reduction, Financial Sector Accounts and International Development (FSAID), and Business Statistics Transformation (BST). The evaluation focused on the period of delivery of ARIES 2.0, from April 2022 to March 2025. Several ARIES programme objectives will continue through the implementation of the ONS’ Strategic Business Plan which encompasses the recently published Economic Statistics Plan, focussed on provision of high quality of core economic statistics.

Findings

Overall, the evaluation found that many projects achieved their outcomes, including improvements in quality and efficiency; improved user experience, decision-making and timesaving; early signs of improvements in capability of the ONS workforce; and a step change in technological resilience.

The evaluation identified the following factors as ‘what worked’ in projects: clear understanding and direction; quality assurance and feedback mechanisms; flexibility and adaptability; as well as multidisciplinary teams and a unified culture. Conversely, the following factors posed challenges: complexity and insufficient planning; unrealistic deadlines and pressure; communication barriers; and resource constraints.

The ARIES project delivery benefited from strong collaboration and a shared understanding across teams. Early stakeholder engagement and structured governance also helped align outputs with user needs.

Nevertheless, recruitment and retention challenges within ONS led to persistent skills gaps and under-resourcing. Internal governance within some projects lacked clarity, causing confusion around roles and decision-making. Ambitious timelines and rigid funding structures also limited flexibility, especially for complex or interdependent projects.

Methodology

The evaluation of the ARIES programme was comprised of an implementation process evaluation (IPE) and a qualitative impact evaluation (QIE), designed to understand both how the programme was delivered and the factors driving its outcomes. The IPE examined decision-making, resource allocation, and barriers, while the QIE used a realist informed approach to develop mechanism-based claims and identify broader impacts.

Primary data for these claims was gathered through depth interviews and focus groups with participants within the ONS and external to the ONS (e.g., government

departments). Participants were sampled purposively and triangulated with secondary evidence from ONS documents. Evidence for each claim was then qualitatively assessed by the NatCen research team, and validated with the ONS staff in claims workshops.