Gera Affordability Ratio — Methodology

The Gera Affordability Ratio (GAR) is a reproducible, published-data-only metric that computes the share of gross monthly income consumed by average rent, per occupation and UK region. This page documents the formula, sources, join logic, and limitations.

Formula

Data sources

Join logic

ONS ASHE Table 15(4).7a uses eleven UK region labels. ONS PIPR and UKHPI use the same eleven geographies under slightly different label forms. The join key is:

Northern Ireland is excluded: no PIPR regional sub-table exists for NI. Only rows where all three sources (ASHE salary, PIPR rent, UKHPI house price) are present for a given occupation × region pair are included. No null-as-zero substitution.

Worked example

These are real published figures, not illustrative numbers. The same arithmetic is applied to all 38 occupations × up to 11 regions.

Limitations

• Gross vs net pay: GAR uses gross salary. On a net (take-home) basis the ratio would be higher. Individual deductions (pension, student loan, tax code adjustments) are not modelled.
• Regional averages: Both ASHE salary and PIPR rent are regional averages. Within-region variation can be large (e.g. inner London rent differs substantially from outer London).
• Full-time employees only: ASHE Table 15(4).7a covers full-time employees. Part-time or gig-economy workers in the same SOC title typically earn less.
• All-property rent: The GAR_rent uses the "all property types" average rent unless the bedroom-specific figure is shown. This may overstate or understate affordability for specific household configurations.
• ASHE suppression: ONS suppresses cells where the estimate is unreliable (CV > 20%). These region × occupation pairs are excluded. Some occupations therefore have fewer than 11 regional data points.
• GAR_buy ≠ mortgage affordability: The Gera Buy Ratio is a simple price-to-income multiple. Actual mortgage affordability depends on deposit, lender income multiples (typically 4–4.5×), interest rates, and credit history.

Frequently asked questions

Why use gross salary rather than take-home pay?

ONS ASHE publishes gross (before-tax) earnings; net pay would require applying HMRC Income Tax bands and National Insurance rates, which vary by individual circumstances (pension contributions, marriage allowance, student loans, etc.). Using gross pay ensures the ratio is reproducible from two official published figures without additional assumptions. The GAR on a net basis would be higher. Users can apply the GeraJobs Take-Home Pay calculator to estimate a net-basis ratio for their specific situation.

Why is Northern Ireland excluded?

ONS PIPR does not publish a regional monthly rent breakdown for Northern Ireland in the same table format used for English regions + Scotland + Wales. A UK total exists but no region-level PIPR row for NI allows a clean join. Including NI would require a different rent source with potentially inconsistent methodology.

Why does ASHE say "East" but the page says "East of England"?

ONS ASHE Table 15(4).7a labels the eastern English region simply as "East". The ONS PIPR dataset and UKHPI both label the same geography as "East of England". Pages display "East of England" for clarity but the join is made on the ASHE "East" row.

How often is the Gera Affordability Ratio updated?

The salary denominator updates annually (ONS ASHE is published each November for the preceding April reference period). The rent numerator (ONS PIPR) publishes monthly; the current dataset uses the May 2026 edition. House prices (UKHPI) also publish monthly; the current dataset uses April 2026. Gera will refresh all three components when the next ASHE release (November 2026) supersedes the current provisional data.

What is the ONS "30% affordability threshold"?

The ONS Private Rental Affordability publication (FYE 2024) states: "An area is considered affordable if median rent is no more than 30% of gross earnings." The Gera Affordability Ratio applies the same threshold to occupation-region pairs: GAR ≤ 30% = "Affordable", 31–40% = "Tight", > 40% = "Unaffordable".

Does the Gera Affordability Ratio differ from the official ONS ratio?

Yes. The ONS official "Private rental affordability" series divides rent by the modelled median income of private-renting households (which differs from the ASHE full-time median because it includes part-time workers and household rather than individual income). The GAR uses ASHE full-time individual gross pay as the denominator so it is directly comparable across occupations. This makes it occupation-specific; the trade-off is it is not directly comparable to the ONS headline affordability ratio. Official ONS FYE2024 headline figures (England 36.3%, London 41.6%) are cited as context on the hub page.