Ooh, fun thread. Having done the PhD mill, I think mine would be about the relationship between the life of the folksinger and the choice of lyrics used in songs like Pretty Polly that have more than 5 known versions. Why, because it sounds like fun and might take forever (I would never have left grad school of my own accord!) - How, well, I'll have to think about that. Quantifying the unquantifiable has always been my strong suit...