The backlog of need among existing households is easier to measure through surveys but may be numerically less important than needs from newly forming households, and some existing needs can be met in situ or within the existing housing stock. It is desirable to try to align measures used in surveys with the criteria of unsuitability of accommodation which are used to prioritise individual households in the allocation process. Such estimates reflect relatively volatile economic variables and should be subject to sensitivity tests. It is difficult to monitor all flows in the local housing market, particularly in relation to private renting and migration. While assessments do look forward over 3-5 years, this involves projecting numbers based mainly on current conditions.
Supply can be as important as demand in determining net needs for additional provision.
In addition, stock condition assessments are relevant to the investment requirements for regeneration, including both refurbishment and the possibility of demolition with or without replacement. Judgement is needed in translating needs assessments into policies in the light of available resources and the range of options available in different tenures and neighbouring areas. Most local authorities now periodically commission housing needs surveys. This development has been strongly encouraged by the planning system and the advice given by Government Regional Offices and Planning Inspectors. Surveys cost on average 25,000 and 'best practice' may require more, although there is a competitive market of consultants offering to carry out such surveys.