FAIR data…Much Bigger than the MAC

Today the Migration Advisory Committee (MAC) published an open letter to the Home Secretary calling for better data access to underpin migration policy. The recommendations are clear, specific, and, however you feel about the UK’s current immigration policy, point to a much broader truth: the UK's ability to make evidence-based policy decisions is constrained not just by what data exists, but by how well that data is described, linked, and governed. Policies and legislation can be put in place, but they can become meaningless if the data isn’t available to support implementation.

At MetadataWorks we work with our clients to make data Findable, Accessible, Interoperable, and Reusable — the FAIR principles that sit at the heart of good data practice. Reading the MAC's letter, we recognise the problems immediately.

Three recommendations, one root cause

The MAC makes three specific asks:

Consistent application-level identifiers across all visa routes. Without a common identifier applied uniformly, linking a main applicant to their dependants, or tracking outcomes across different systems is either impossible or depends on unreliable workarounds. This is a classic interoperability failure. Identifiers are metadata. Without consistent, well-governed identifiers, even the richest datasets become islands - the MAC is essentially stating that the department is being asked to use data they simply can’t get hold of or link to.

Sponsor information captured with National Insurance numbers. The Family route assessment currently lacks visibility of sponsor income and household circumstances because the data simply isn't collected in a structured, linkable form. A National Insurance number is a key that unlocks connection to HMRC records — but only if it's captured consistently and stored in a schema designed for linkage rather than just for administrative processing. Again - an ‘easy’ bit of background research becomes essentially impossible if the information isn’t findable.

Extending HMRC-Home Office linkage to DWP. The recent HMRC-visa data linkage is a genuine step forward for MAC, but its utility would multiply significantly when combined with benefits data. This is federated data in action: no single department holds the full picture, but with the right metadata standards and linkage infrastructure, the picture can be assembled.

Each of these problems, at its core, is a metadata problem. Inconsistent identifiers, unstructured reference fields, and siloed administrative systems are all symptoms of data that was designed for operational purposes — processing applications, paying benefits, collecting tax — rather than for analysis and reuse.

This is bigger than migration

The MAC is careful to note that better data "will support others beyond the MAC in building the wider evidence on the impacts of migration." We'd go further: the infrastructure improvements they're calling for would benefit every cross-government analytical team trying to answer questions that span departmental boundaries.

The MAC's letter is about migration and the issues the department has in following guidance when the information at hand isn’t readily available. But the solution is much bigger, its about building a government data ecosystem where assets are catalogued, standards are shared, and linkage is by design rather than by exception.

What good looks like

The good news is that this is a solved problem — at least technically. The FAIR data principles, now widely adopted across the research and public sector data communities, provide a clear framework. Data that is:

• Findable: catalogued with rich, consistent metadata so analysts know what exists
• Accessible: available through secure, governed access pathways rather than ad hoc data requests
• Interoperable: described using shared standards and identifiers that allow linkage across systems
• Reusable: documented well enough that a new team can understand and work with it without starting from scratch

The MAC's three recommendations map almost perfectly onto the I and R of FAIR. Consistent identifiers (Interoperability). Structured sponsor fields (Reusability). HMRC-DWP linkage (Interoperability again).

The missing piece in most government data programmes isn't ambition or even investment — it's the metadata governance layer that makes these linkages trustworthy and sustainable over time.

A call to action

We welcome the MAC's letter and hope the Home Office responds with consideration, but implementation will require more than agreement in principle. It will require:

• Defined metadata standards for each of the recommended fields, agreed across departments
• A governance process for maintaining and updating those standards as visa routes change
• A data catalogue that makes the linked datasets discoverable to authorised analysts across government
• Ongoing publication of analysis, as the MAC rightly requests, to demonstrate value and build the case for further investment

These are exactly the kinds of challenges MetadataWorks was built to help with. We've supported organisations including the ONS, NHS England, ADR UK, and NISRA in building data catalogues and metadata governance frameworks that make cross-departmental data sharing not just possible, but routine.

If you're working on government data infrastructure and want to talk about how better metadata management could support your work, contact us, we'd love to hear from you.