How many cinemas in Rotterdam screened films in 1931?
This is an example of a simple question that can be answered easily by using Cinema Context. A question like this one is particularly interesting in comparison with other cities and other years. This is sometimes a necessary first step that must be made in order to answer more complex questions.
Enter 'Rotterdam' in the first search field and select City from the pull-down menu behind it
Enter ‘1931’ and ‘1932’ in the search fields marked programmes between
Search results will list ‘1 to 10 of 19’. This means that 19 cinemas have been found that match your search query.
Based on this result, you can pose a number of questions:
What is your definition of a 'cinema'? Not every building where a film is screened is necessarily a cinema. Is a theatre that only screens a film occasionally a cinema?
A travelling cinema listed within Cinema Context is not a building, but a company that travels from city to city and screens films. Sometimes that would happen in a building, and sometimes in a fairground booth. You can search for travelling cinemas in the collection Programmes or Companies.
What counts as an operational cinema? Would you include cinemas that were closed for renovations for a large part of a year?
Even relatively simple questions like this one yield results that are not entirely unambiguous. You will always have to question your own assumptions.