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Message:: [QUOTE="Cringely, post: 2057173, member: 22271"]The Sheldon linear scale (Price = constant x grade) broke down within a few years of the publication of Early American Coppers. If we look at price versus adjectival (Good, VG, Fine, VF, EF, AU, MS60, & MS63) and plot adjectival grade (not numerical) vs. Price (on a semi-log scale), you actually will see a reasonably linear relationship. This relationship has held pretty much linear for over 30 years (e.g., 1981 - 2011). For type coins, each step up in grade is usually accompanied by a ~75% increase in price (obviously this slope will vary depending on the coins series. For example, if you look at the different series of Large Cents, you will see that the slope (increase in price for each step up in grade) will vary (these are relative price increases for an arbitrary year between 1981 and 2012—while the absolute price of a VF-20 coin will vary, the price of an EF-40 relative to the VF-20 stays pretty much the same):Chain    67 ± 8%Wreath    65 ± 3%Liberty Cap    79 ± 9%Draped Bust    106 ±10%Classic Head    111 ±8%Coronet    79 ±12%Braided Hair    76 ±16%85-coin Red Book Type Set (excludes clad coins)   75 ± 4% The data has been published in three articles to date:——“Pricing Relationships of United States Type Coinage”, The American Journal of Numismatics Second Series, 23, 257 – 263 (2011)——“The Sheldon Scale and Price-Grade Relationships in Large Cent Type Coinage”, Penny-Wise (publication of Early American Coppers), XLVI, 5 – 15 (2012)——“The Sheldon Scale and Price-Grade Relationships in Half Cent Type Coinage”, Penny-Wise (publication of Early American Coppers), XLVI, 31 – 39 (2013) As to why the behavior is exponential (semi-logarithmic), I don't have a clue. All I know is that the pricing relationship has held pretty constant.[/QUOTE]

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