The preliminary steps toward the actual valuation of any given parcel of property are:

The determination of the value of a single city lot 25x100 situated midway in the block on the street or avenue wherein lies the property to be appraised, and from this unit of value deducing the value of that property as a whole.

 Example for Four Lots Unit of value on 4th Avenue........ Lot at center line........................... \$10,000 Next lot ................................... 10,000 To lot adjoining corner add 10% of unit, \$10,000 + \$1,000 = ...................... 11,000 Corner lot is worth \$11,000 plus 60%, or..... 17,600 \$48,600 Add plottage 10%........................... 4,860 Total valuation...................... \$53,460

How do we arrive at the proportionate differences of value between these four lots which enables us to say that one lot is worth 10% more than the one alongside of it and not 15% to 20% more, and that the corner lot is worth 60% more than the adjoining lot and not 50% or 100% more? These relative values are approximations, and are the result of much observation and the analysis of prices obtained at public auction and private sales.

Let us take a concrete example illustrating the reason for the conclusions referred to: In 1906 at a public auction sale of vacant lots in the Borough of the Bronx on Jerome Avenue, east side, between 208th and 209th Streets, several individual lots were sold, each bringing \$2,800. At the same time a plot 100x100 at the northeast corner of 208th Street and Jerome Avenue was sold as a whole for \$15,100. The sale price of individual lots gives us the unit of value. Let us apply it in the manner I have stated to be customary with appraisers:

 Example Unit of value lot at center line............... \$2,800 Lot adjoining corner, add 10% to \$2,800............ 2,800 Lot adjoining corner, add 10% to \$2,800..... 3,080 Corner lot add 60% to \$3,080................ 4,928 \$13,608 Add plottage 10%................................ 1,360 Total....................... \$14,968

which is approximately the price actually obtained for the plot 100x100 as a whole. At this sale all the conditions were present which make this example fairly applicable in support of the theory.

There are, however, exceptions to this theory of relative values. In factory districts it is often the case that the value of the corner lot is rated at only 50% more than the value of the lot adjoining. This is due to the fact that the relative value of the area to the frontage is greater in factory lots than it is in lots the availability of whose entire area is limited by law, or in lots where window display would make the frontage relatively of greater proportionate value than the area.