compared to when they were first used one of the key problems with telephone polls is the
Opinion poll In some places many people have only mobile telephones. Because pollsters cannot use automated dialing machines to call mobile phones in the United States (because the phone's owner may be charged for taking a call[27]), these individuals are typically excluded from polling samples. There is concern that, if the subset of the population without cell phones differs markedly from the rest of the population, these differences can skew the results of the poll.[28]
Former Australian dialling codes In Australia, as in other countries, due to the increase in subscriber uptake of services such as extra telephone lines in homes, mobile phones and other services, the previous numbering plan was being stretched to its limit. It was decided to reduce the number of area codes and lengthen all subscriber numbers by one or two digits. This occurred between 1994 and 1998, and was done progressively to ensure as little inconvenience and confusion as possible. The gradual change was also to avoid number clashes, a situation where two subscribers in two completely different locations have technically the same telephone number if dialled in their entirety. The first numbers to be converted to eight digits were numbers in the 99x xxxx and 99 xxxx ranges in the suburb of Mona Vale in Sydney, which all became 999x xxxx or 9999 xxxx on 25 July 1994. The final codes changed to eight digits were the Queensland (070), (071), (076), (077) and (079) codes, which all changed to (07) 4yxx xxxx on 10 November 1997.