Travel and tourism play an important economic role. Yet, compared to other countries, international travel to Switzerland has declined: the 5th most visited country in 1950, it is now only the 35th most visited. The project will investigate factors which may explain these long-run variations. Four trends will be investigated: catch-up growth, population aging, migration and environmental changes. The first two trends will be analysed in details for the first time. As an application, the project will provide long-run projections of international travels towards Switzerland from a selection of representative foreign countries, based on expected variations in the four trends.