Measuring environmentally sustainable tourist behaviour

•It is not known how many tourists display environmentally sustainable behaviour.•Estimates in this empirical study vary from 0% to 44%.•Responses are affected by how tourists are asked about their behaviour.•And by whether the definition of such behaviour includes intent.•More observational studies are urgently needed.

This study reveals substantial variation in estimates of the proportion of tourists behaving in an environmentally sustainable manner. Results indicate that the variation is explained by (1) definitions of environmentally sustainable tourist behaviour including—or not including—intent to protect the environment and (2) the use of either unprompted open-ended or prompted closed questions. The latter are associated with respondent’s tendencies to respond in a socially desirable way, thus artificially inflating the occurrence of environmentally sustainable tourist behaviour by as much as 74 per cent. Unprompted open-ended questions are not susceptible to social desirability bias. Future studies into environmentally sustainable tourist behaviour should measure actual observed behaviour. If this is not possible, unprompted open-ended approaches are recommended.