Associations are organizations of people who work in a certain industry, market, or occupation, and can be local, national, or international in scope. They typically gather and publish data on their industries, some of which may be available for no charge on the association website. Associations can be located by methods such as guessing their name in a Google search - "national restaurant association" - or looking in a directory of trade associations, such as Encyclopedia of Associations.
A few examples related to tourism: