It cannot provide information about the use of taxis by others, like tourists from abroad: such information is unavailable.Because the NTS's Scottish sample size is not large, and because only a small proportion of journeys involve the use of a taxi, the NTS's Scottish samples for seven years had to be combined in order to obtain a sample of taxi trips which was large enough to produce these statistics. As with all surveys, the results could be affected by factors such as sampling variability and non-response bias.