Senior tourism starts to fully develop when the interest in travelling has increased among people of higher ages.

当高龄者对旅行越发感兴趣之际，银发旅游开始全面发展起来。

The development of senior tourism is mainly caused by demographic changes, especially in developed countries.

银发旅游之所以发展，主要是因为出现了人口变动，尤其是在发达国家。