Thinking through funnels of attrition
When first introduced to the idea of a funnel of attrition (my early attempt at a slightly more nuanced and symmetric — but still generic — version is here), I largely thought of it as a useful heuristic for thinking about sample size calculations, by being forced to think about issues of awareness and take-up as well as a few steps along a causal chain between initial participation or use and longer terms outcomes of interest.
More recently (including here), I have tried to use it as a tool for thinking about articulating assumptions in a theory of change about where people might ‘fall out of’ (or never join) an intervention, thus leaving the funnel. More specifically, I tried (along with colleagues) using it as a goal for a conversation with implementing partners (that is, “let’s map out the funnel of attrition”), tackling the question from multiple perspectives. Various perspectives were brought in using personae, which I created beforehand relying partially on average results from the baseline as well as some stylizing to try to bring certain features into the conversation. At first I feared being overstylized but, in the end, I think I had too little detail. I reviewed my notes from The Inmates are Running the Asylum and was reminded of the importance of specificity, even at the expense of accuracy.
I liked this idea for guiding a conversation because the funnel of attrition is a little more straightforward than a full theory of change but, in constructing it, you still end up articulating some central assumptions, which can be added to thinking about change may/not happen. It seems like a handy building block in a well-considered theory of change.