However, because of problems of definition, which directly affect statistical measurement, it is not possible with any degree of certainty to provide precise, valid or reliable data about the extent of world-wide tourism participation or its economic impact.

然而，由于直接影响统计测量的定义问题，不可能提供关于全球旅游参与程度或其经济影响的准确、有效或可靠的数据。