Clearly all of the population indices, measures, and associated interpretive methods laid out in this chapter are fraught with empirical and theoretical difficulty. The derivation of population estimates or indices from surface data is a difficult and contentious undertaking (cf. [Fish and Kowalewski 1990,Tolstoy and Fish 1975]). Nothing about it is straightforward. Like Flannery, though, I prefer to light one small candle rather than curse the darkness ([Flannery 1976a]: 165). The method I have described in this chapter for generating both sector and phase population indices produces values which are sufficiently proportional to actual population to be useful, at least in the Titicaca Basin context. Some of the patterns they reveal are very illuminating indeed, as I hope to show in the remainder of this study.