Price analysis was based on the statistics and prices of more than 50,000
unique diamond listings available via the Internet during the first week of
3.7.1. Market price adjustment
AGSL graded diamonds with Ideal Polish and Symmetry are often priced about 8% –
10% higher than similar GIA-GTL graded diamonds with Excellent/Excellent
symmetry and polish. However this differential fluctuates over time and carat
weight ranges; a week later than this survey’s analysis period, equivalent
GIA-GTL and AGSL listed diamonds in the 0.6-0.69 carat range averaged out at
the same price. The relatively small numbers of these stones, and the niche
nature of this business, means the various margins of a small number of vendors
can have a large effect on the average price results.
A number of the diamonds in this survey were not graded as AGS 0 by AGS; these
diamonds trade at a lower premium to GIA stones. This has been taken into
account in the pricing of these stones.
EGL graded diamonds are currently offered within the trade at 9% – 15% lower
than the same grade GIA-GTL stones. Our statistics
show little (within ±3%) difference in prices for diamonds graded by EGL USA
and EGL overseas, although anecdotal evidence suggests a larger differential.
Table 2. An example (using stone # 3) of the method used to calculate
the market price comparisons in Table 3.
|E.g. stone # 3||GIA||EGL|
|Number of stones in database||85||54|
 The only way to automatically
differentiate listed diamonds graded by EGL USA from EGL in other countries was
by the grading report numbers; EGL USA report numbers start with ‘LA’, ‘US’ or
‘7’, or end with ‘D’. At the time of this survey there were some 2,500 diamonds
in Pricescope database with EGL grading reports that satisfied this condition
and about 4,100 listings with EGL reports with numbers that did not. Report
numbers were not available for all EGL graded diamonds.