What are LSOAs and MSOAs?

Why not just use postcodes or wards

Postcodes are designed for delivering mail and can change frequently. Electoral wards are designed for representation and can vary a lot in population size. Neither is ideal as a stable, consistent unit for statistics.

To solve this, the Office for National Statistics created Super Output Areas. These are designed specifically for statistical work.

Lower-layer Super Output Areas (LSOAs)

LSOAs are small areas that usually contain around 1,500 residents. They are:

• Similar in population size, which makes comparisons more reliable
• Designed to be stable over time, changing only when needed
• Used across many datasets, including IMD, health, housing and education statistics

Each LSOA has a code such as E01001234. These codes appear in data files and mapping resources.

Middle-layer Super Output Areas (MSOAs)

MSOAs are larger areas made by grouping several LSOAs together. They usually contain around 7,500 residents.

MSOAs are used when analysts need:

• More stable statistics based on larger populations
• Maps that give a broad overview rather than very fine detail
• A compromise between small area and local authority level data

How LSOAs and MSOAs relate to IMD

IMD is calculated at LSOA level. Each LSOA receives an IMD score, rank and decile. These results can then be:

• Mapped directly at LSOA level
• Aggregated up to MSOA level or other geographies using summary measures
• Linked to other datasets that use the same codes

Understanding LSOAs and MSOAs makes it easier to combine IMD with other sources such as health outcomes or school results.