Dear list, There was life before Davenport. The concept of unearned increment is often traced back to J.S. Mill. Here is one of his sallies: "Suppose that there is a kind of income which constantly tends to increase, without any exertion or sacrifice on the part of the owners: those owners constituting a class in the community, whom the natural course of things progressively enriches, consistently with complete passiveness on their own part. In such a case it would be no violation of the principles on which private property is grounded, if the state should appropriate this increase of wealth, or part of it, as it arises. This would not properly be taking anything from anybody; it would merely be applying an accession of wealth, created by circumstances, to the benefit of society, instead of allowing it to become an unearned appendage to the riches of a particular class. Now this is actually the case with rent. The ordinary progress of a society which increases in wealth, is at all times tending to augment the incomes of landlords; to give them both a greater amount and a greater proportion of the wealth of the community, independently of any trouble or outlay incurred by themselves. They grow richer, as it were in their sleep, without working, risking, or economizing. What claim have they, on the general principle of social justice, to this accession of riches?" Mill, of course, used "rent" as Quesnay, Smith, Ricardo, et al. had long done, to mean the net income imputable to land. The many confusing usages of the term Pat refers to came along later, in transparent efforts to diffract the unwelcome light Mill et al. shone upon ground rents, and blind students to the obvious. Marshall had no problem with the concept in an urban setting, and in his Appendix G and elsewhere explains two or more practical methods of determining site values. In recent usage, "unearned increment" generally refers unambiguously to the rise of the selling price of land, whereas Mill wavers between that and a rise of rents. Pat fails to respond to my request that he tell us what he means by his terms. Agents in the land market estimate rents and land prices continuously. So do tax assessors. There is a vast literature on appraisal and assessment. Foresters, ever since Martin Faustmann (1849) know how to calculate the rents and values of forest sites, which they routinely divide and map into "site classes" of varying productivity. I will be giving a paper on this at Grinnell this June 25. There is no call for Pat to treat this as some kind of unplumbed mystery. Mason Gaffney