The other day I read a useful paper about causation, by Kenneth Waters, who is now at the University of Calgary. At least I found it useful. Every so often I’ll make a dive into philosophical literature on causation, and the recurrent problem that I find is that philosophers are generally preoccupied with causation for single events (examples of balls hitting other balls and convoluted assassination schemes) or for big generalizations about classes of events. Meanwhile, sociologists regularly form their causal questions as about differences between groups of persons, as in wanting to explain why whites score higher on standardized tests than blacks or why women live longer than men.
Waters explicitly tries to formulation insights about causation in population terms. As he puts it:
Focusing attention on singleton situations about a single lighting of a match, a single breaking of a vase, or the single catastrophic dropping of a boulder obscures important features of causation. Much light could be shed on causal reasoning by shifting attention to causes in populations.
To get there, he draws a distinction between potential difference makers and actual difference makers. The key move here is the study of actual differences, for which you have to be talking about the causes of multiple outcomes, that is, a population. While potential difference makers are the larger body of causes of an outcome, actual difference makers are the ones for which actual variation in the population in question explains actual variation in the outcome.