Gera Service Price Index (GSPI) — Methodology

What is the Gera Service Price Index?

The Gera Service Price Index (GSPI) is a named, Gera-computed inflation index for UK marketplace service categories. It is set equal to the ONS Consumer Prices Index including owner occupiers' housing costs (CPIH) sub-index value for the most relevant COICOP category, expressed as an index with a 2015 base of 100.

A GSPI of 141.2 (domestic services) means that the cost of domestic and household services has risen 41.2% since 2015, according to the ONS CPIH dataset. This is a published ONS figure, not a Gera estimate.

Data sources

CPIH sub-indices used

GSPI values for January 2026 (2015=100), fetched from the ONS CPIH01 API on 2026-06-20:

Step-by-step formula

1. 1
   Identify COICOP category. Map each service type to its ONS COICOP classification in the CPIH01 dataset. The COICOP code determines which inflation series the GSPI is drawn from.
2. 2
   GSPI = CPIH sub-index value (Jan-26, 2015=100). Query the CPIH01 API: /observations?time=Jan-26&aggregate={CODE}&geography=K02000001. The observation value is the GSPI. No API key required.
3. 3
   YoY% = (GSPI_Jan26 − GSPI_Jan25) / GSPI_Jan25 × 100. Computed from two API calls (Jan-26 and Jan-25 for the same aggregate/geography pair).
4. 4
   Regional labour context (ASHE). Per region, look up ONS ASHE Table 15(4).7a median gross annual pay for the primary trade SOC 2020 code. Implied hourly rate context = annual_pay ÷ 1,760 working hours. Where ONS has suppressed a cell (too few observations, marker "x"), the national median is used. ONS-suppressed cells are never interpolated.
5. 5
   N<5 honesty floor. If Gera-crawled quote data is available, any region × service cell with fewer than 5 quotes shows "insufficient data" for the quoted median. This cluster currently operates in CPIH-only mode — all price context is index-based, not a quoted price.

Important caveats

• ⚠GSPI is an inflation index, not a price quote. It shows how much costs in a category have risen since 2015. It does not tell you what a specific job will cost you today. Get quotes from tradespeople.
• ⚠ASHE hourly rates are indicative context only. They are median full-time employment wages, not self-employed trading rates or callout charges. Actual callout fees, materials, and travel vary.
• ⚠ONS CPIH covers Great Britain (England, Scotland, Wales). Northern Ireland data is included in the published national index but may not be separately available at sub-category level.
• ⚠No specific lender, insurer, or provider product is quoted.All figures are generic ONS aggregate series. Gera does not quote individual provider prices.

Service types covered

25 service types, each mapped to a real CPIH COICOP code: