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