Peter Stillman writes that "in the agricultural societies of old (including of 620 AD in Arabia), the produce of the land was a surrogate (and easily measurable) indicator of income, and that now, in non-agricultural societies, we use income because produce of the land is meaningless (or zero) for the many non-agricultural types." He issues the last line ex cathedra. It is, I believe, seriously wrong and misleading. I have heavy documentation on hand, and will supply it to anyone who asks. Mason Gaffney