It is widely recognized that the current state of statistics on international tourism is far from satisfactory in the case of most countries, and that inter-country comparisons are extremely difficult because of limited consistency among the definitions and classifications employed by different countries. Deficiencies in statistics arise from the intrinsic difficulties both in defining the concepts and classifications and in collecting sufficiently reliable data. Work on statistics and economics of tourism is comparatively recent, in contrast to statistics of population, labour, international trade and industrial activity, in which there is long-term experience. Each country has its own geographical and administrative conditions which have affected the growth of tourism statistics. Moreover, these statistics have usually received low priority in the development of a national statistical system. Many of the items of data must be collected from establishments dealing with visitors to a country or from international visitors themselves, who are not the easiest respondents for statistical inquiries, partly because their transactions may be carried out in a variety of currencies and not always in accordance with government regulations. The commercial export or import of merchandise is usually accompanied by considerable documentation, which furnishes the basis for compiling international trade statistics. By contrast, most countries, in order to facilitate tourism, have minimized or even eliminated formalities and record-keeping concerning international visitors at frontiers and other points of contact. The volume and geographical dispersion of tourism also makes collections of detailed statistics difficult in many cases.
Even in countries with advanced systems of statistics and considerable experience in this field, the available statistics of tourism are far from complete and there are marked difficulties in reconciling certain data from different sources. While the growth of the tourist industry is of major importance to many developed countries, they have serious difficulties in compiling statistics of tourism that are adequate to their needs partly because of their limited statistical resources.