Sources of housing supply data used by the Greater London Authority

Introduction
This note sets out the two measures of housing supply used by the GLA, reflecting the different targets set out in the Mayor’s London Plan and London Housing Strategy.

London Plan
The housing provision targets set out in the London Plan are defined in terms of total net housing supply, comprising three components:
– Conventional completions: self-contained homes from new build, conversions or changes of use
– Non-conventional completions: non-self-contained housing such as bedrooms in hostels or halls of residence
– Change in long-term empty homes (those empty for more than six months), where a decrease is an addition to supply and an increase is a subtraction.

Progress against these targets is monitored in the London Plan Annual Monitoring Report, the latest edition of which was published in 2018. The source for conventional and non-conventional completions is the London Development Database (LDD), a uniquely detailed database of housing developments created from data provided by London borough planning departments and checked by the GLA. The number of long-term empty homes is monitored using annual statistics reported by the Ministry for Housing, Communities and Local Government (MHCLG), based on local authority Council Tax data.

In 2016/17, the latest year for which data is available, the total net housing supply in London was 45,505, comprising 41,371 conventional completions, 4,526 non-conventional completions and an increase of 392 in the number of long-term empty homes.

The conventional component of total housing supply is reported by the GLA to MHCLG who publish it as part of their national statistics on the ‘Net supply of housing’.

MHCLG also publish quarterly national statistics on house building. These statistics are not strictly comparable to the conventional housing supply statistics published by GLA or MHCLG themselves, as they cover only new build developments and are reported on a gross rather than net basis. They are also known to undercount even new build completions. They can however be a useful indicator of future trends in completions when these caveats are borne in mind.

London Housing Strategy
The affordable housing targets set out in the London Housing Strategy are monitored using MHCLG’s national statistics on affordable housing supply. These statistics cover not just new build but also acquisitions of existing private sector homes for affordable housing. They are released on an annual basis with a lag of several months, and combine data from a range of sources including GLA programme monitoring statistics.

The GLA funds the majority of affordable housing supply in London, and publishes its own statistics on its programme on a monthly and annual basis, with a shorter time lag than MHCLG. The most recent GLA statistics show that in 2017/18 there were 12,555 affordable homes started in London with GLA funding, and 5,355 completed. According to MHCLG’s statistics, when taking into account homes funded from other sources there were 14,202 affordable homes started and 7,135 completed in London.