The value of books determined by the Rare Book Sale Monitor (RBSM) is achieved by selecting comparable sales and adjusting the prices according to the differences between the comparable sales and the item being evaluated. RBSM comparative pricing is produced by adjusting the sale price of a particular title that is closely monitored, by accounting for any variation from the pre-established baseline. Every recorded sale is compared against a baseline set of data necessary for the valuation process to commence. When available, extra information may be incorporated as long as it is considered to be a positive or negative valuation factor.
The complete set of required descriptions includes:
A. Name of the author(s), artist(s), editor(s),
B. Title or subject matter,
C. Publisher edition, printing, impression,
D. Date published,
E. Binding (hardcover, wraps, leather, rebound etc.),
F. Signed or inscribed by the author(s), artist(s), and
G. The physical condition of the book including restoration.
In addition, any of the following descriptions are accounted for but not required:
H. Any marks, signatures, or labels on the item,
J. Reference source citing the item, and
K. History (provenance) of the item,
The factor by which each of these unique attributes affects valuation varies by the genre and sometimes by the specific title within the category. The following are a few generalizations that the RBSM recorded with statistical significance:
1. The scarcer a title is, the less significant the factor of edition/printing/impression will be. For example, for quite some time now sale prices for the first editions of J.R.R.Tolkien’s books have shown a steady increase. This market trend has now begun to widen across other editions of these same titles. This “Over-the-Top” effect is predominant in the cases of extremely scarce titles that due to exorbitant pricing are facilitating the sale of their second or third editions or other related publications.
2. Another factor that gets to be less significant as the book gets more scarce is the factor of condition. The condition of a book usually carries a great influence on its value. While physical condition and the extent of restoration have a significant effect on the value, it seems that collectors are less likely to turn down the opportunity to acquire some of the more scarce titles despite their less than perfect condition.
In order for the RBSM to account for these non-linear representations, in addition to the data attributes referenced above, the following ranking variables are also in use:
L. Scarcity (no availability, less than 3 comparables available, less than 10 available for sale),
M. Price Track (Super High, Very High, High), and
N. Sales Velocity (more than 1 sold during the last month, more than 1 sold during the last 2 months, more than 1 sold during the quarter).
While A & B are primarily measures of the availability or the supply of a particular title, C is a measure of the frequency that a particular title is traded. An increase in “sales velocity” has a short-term effect on pricing and it is interpreted by the RBSM as a “circuit breaker” in order to filter out impulse trading from affecting longer-term trends. Similarly, the price an item sold for in an auction carries by default, a higher sales velocity due to the fact that auction sales involve bidding duels.
The following representations derived from the RBSM algorithm serve as a quarterly indicator of sales traffic and the effect it had on the pricing of the corresponding author titles and the genre as a whole.