# What each postcode district specialises in

> A concentration score separates a genuine sector tilt from districts that simply register many companies.

- Category: Money
- Cadence: monthly
- Status: Published on a monthly cadence.
- Dataset key: `business-sector-specialisms`
- Source: [Companies House](https://download.companieshouse.gov.uk/en_output.html)
- Licence: Open Government Licence v3.0 — [terms](https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/)
- Canonical page: [https://londongraph.com/g/business-specialisms-by-postcode](https://londongraph.com/g/business-specialisms-by-postcode)
- Machine-readable record: [https://londongraph.com/data/business-specialisms-by-postcode](https://londongraph.com/data/business-specialisms-by-postcode)

## Methodology

Each cell is a location quotient: the sector's share of active companies in that postcode district divided by its share across all mapped London districts. One is the London average; two means twice the average concentration. The display selects leading specialist districts with at least 20 matched companies, while downloads retain every shown cell. Registered-office and self-declared-SIC caveats still apply.

## Visualisations

- [Heatmap](https://londongraph.com/g/business-specialisms-by-postcode): A concentration score separates a genuine sector tilt from districts that simply register many companies.
- [Map](https://londongraph.com/g/business-specialisms-by-postcode?view=geography): Compare the same measure geographically.
- [Distribution](https://londongraph.com/g/business-specialisms-by-postcode?view=distribution): Place every mapped area in the selected measure's distribution while preserving missing values.
- [Profiles](https://londongraph.com/g/business-specialisms-by-postcode?view=profiles): Read each row as an aligned trend rather than a colour cell.

## Citation guidance

Attribute the original publisher named above and identify LondonGraph as the visualisation and methodology layer. Do not describe live values as a historical census, and do not present placeholder values as observations.