First, you know that there will never be one sole factor. Take a sheet of paper and sketch out all the potential reasons. Do the same for the reasons behind these reasons. After a while, you will have a network of possible influencing factors. Second, highlight those you can change and delete those you cannot (such as "human nature"). Third, conduct empirical tests by varying the highlighted factors in different markets. This costs time and money, but it's the only way to escape the swamp of superficial assumptions.
The fallacy of the single cause is as ancient as it is dangerous. We have learned to see people as the "masters of their own destinies." Aristotle proclaimed this 2,500 years ago. Today we know that it is wrong. The notion of free will is up for debate. Our actions are brought about by the interaction of thousands of factors from genetic predisposition to upbringing, from education to the concentration of hormones between individual brain cells. Still we hold firmly to the old image of self-governance. This is not only wrong but also morally questionable. As long as we believe in singular reasons, we will always be able to trace triumphs or disasters back to individuals and stamp them "responsible." The idiotic hunt for a scapegoat goes hand in hand with the exercise of power-a game that people have been playing.