In practice, the magistrates are rarely too worried about the question of local need in respect of off-licences, particularly in urban areas, but this is not universally the case. On-licences are a different matter. This is one aspect which may be dealt with in the local policy. In addition, the local policy may indicate how the licensing committee wish to have evidence about local need presented. Often, radius maps are required showing the location of the different types of licensed premises in a limited area, usually a quarter or a half mile radius. In some cases, petitions are produced, attempting to show that local customers would use a shop which sold alcohol in a particular location or currently use a shop and it would be convenient if it also sold alcohol. In practice, petitions are rarely helpful and magistrates are often sceptical about them. Expert market research and demographic profiling evidence or evidence from a licensing surveyor will be much more persuasive but it is much more expensive and rarely commissioned until the applicant knows that he or she is likely to face a problem. It can also help to show that the premises will be selling some form of specialist product such as Indian beer which is not generally available in the area.