Problem (widely addressed by scholars) are at times being highlighted without providing any statistical data.... In this case, should the researcher seek to quantify the problem?
Sometimes the absence of data/evidence for a historical problem is itself part of the issue. Is the absence deliberate, accidental or not considered inportant enough to record by contemporaries. Lack of evidence could be an unwitting historical testimony
Perhaps falsifiable evidence could be found, and one could rule out certain things that have no proofs. Try looking for falsifiable evidence and eliminate what has already been proven to be outside the parameters of what you are seeking. This is dependent on the discipline; scientific, social, cultural etc. If it is science, and if you cannot prove it, then it is speculation. If it is scientific and you are trying to enumerate something without enough valid information you will not quantify it unless it involves a universal theorem or an axiom. There is the universal approximation theorem if you have any base information in a mathematical study. Actually the same goes for the social sciences, but certainly it would be much more difficult to reason out logically than something that is inherently reasonable, rational and logical. You will probably not find reasonable, rational and logical in any social science where there is virtually no historical information that can be quantified or noted.
There is a saying, 'if it doesn't exist, create it.' You could possibly look to oral history sources by conducting interviews. Archives can also be useful.