Five year housing land supply
We are required to maintain a five-year advance supply of land for housebuilding, updated annually. These are the most recent calculations as at June 2019:
| a | Core Strategy and Urban Core Plan (CSUCP) requirement 2019-24 | 3700 |
| b | Requirement minus 2010-19 net undersupply | 4172 |
| c | Requirement including undersupply, plus 20% buffer | 5006 |
| c | Calculated supply 2019-24 from deliverable sites (see note 3) | 5101 |
| d | Calculated supply plus assumed windfall (see note 1) | 5226 |
| e | Total supply as a percentage = 5226/5006 = | 104.4% |
| f | Total supply in years | 5.22 years |
Notes
(1) Before 2017, a windfall assumption (described as "conservative") of 50 dwellings per annum was included. The figure included here has from that date been reduced to 25 per year, to take account of the availability of up-to-date information contributing to the supply in row (d) and the reduction in the minimum site size from 5 or more dwellings to 3 or more dwellings from the 2017 SHLAA onwards.
(2) In contrast to the method used in some earlier years, no explicit allowance is made for bringing empty homes back into use, as the Core Strategy and Urban Core Plan (CSUCP) requirement already takes account of an assumption about reducing the vacancy rate by doing so.
(3) The figure represents the estimated capacity of suitable and deliverable sites, not their estimated date of development as shown in the Trajectory included in the 
2018 Strategic Housing Land Availability (SHLAA) Update [20.56MB] as Appendix 2. The Core Strategy requirement for 2019-24 (row (a) above) is calculated by annualising the five-year net provision totals in CSUCP policy CS10. The calculated supply (row (d) above) is much higher than that shown in the Trajectory in the 2018 SHLAA Update or the 2019 Housing Topic Paper. This is because the calculated supply includes all sites found suitable and deliverable, even though in practice many of them will be delivered beyond the first five years.
For the avoidance of doubt, the 2018 SHLAA Update was carried out too early to take account of the government's alteration of the definition of deliverability published on 24 July 2018, and represented the position at its base date of 31 March 2018. The new definition of deliverability has been taken account of in the 2019 Housing Topic Paper. This is the principal cause of the reduction in the calculated five-year supply since 2018.
