Asscher Diamond Price Index
The transparent measurement framework for future market observations
Current status
The Asscher Price Index is currently a measurement framework, not a published market index. We will not convert directional price estimates into “data” retroactively. A release becomes a measured index only when its raw observation criteria, sample size and summary statistics are retained.
Why build an Asscher-specific index?
Diamond pricing is heterogeneous. A useful Asscher comparison needs to control for more than carat weight: natural versus laboratory-grown origin, color, clarity, grading lab, exact carat band and—in some analyses—proportion or fluorescence filters. Mixing unlike stones can produce a precise-looking number that answers the wrong question.
Minimum observation protocol
| Field | Required | Reason |
|---|---|---|
| Observation date/time | Yes | Prices and inventories change. |
| Retailer/source | Yes | Allows source-level diagnostics and deduplication. |
| Natural/lab-grown | Yes | These are separate markets. |
| Carat | Yes | Primary size/weight control. |
| Color + clarity | Yes | Material price drivers. |
| Grading lab/report | Yes where available | Quality comparability and verification. |
| Price + currency | Yes | Raw market observation. |
| Length/width/depth/table | Preferred | Supports spread/proportion analysis. |
Recommended published statistics
For each sufficiently populated cohort, report the sample count, median, 25th percentile and 75th percentile. Avoid publishing a cohort when the sample is too small to be useful. Do not mix currencies without recording the exchange-rate convention and observation date.
Publication thresholds
These are AsscherDiamond.com editorial data-quality rules, not industry standards:
| Included listings | Publication treatment |
|---|---|
| Fewer than 10 | Do not publish a cohort median as a market reference; describe the sample as too small. |
| 10–24 | May publish as an exploratory observation only, with the exact sample count prominently shown. |
| 25+ | May publish median and quartiles when the cohort definition, raw rows and deduplication rules are retained. |
Listings that appear to represent the same grading report should be deduplicated before summary statistics are calculated. Out-of-stock or unavailable listings should not be treated as current offers unless the release explicitly studies historical inventory.
Example cohort definition
Download the observation template
Relationship to the current Price Guide
The existing Asscher Diamond Price Guide contains directional editorial ranges. Those ranges remain useful for orientation but are explicitly not represented as measured medians because the original edition did not preserve an auditable raw sample. When the first reproducible index observation is published, the Price Guide should link to that release and clearly label the observation date.
Versioning rule
Every measured release should preserve a version identifier, observation date, methodology version, cohort definition and sample count. Older releases should remain accessible so changes over time can be audited rather than overwritten.
What a future measured release must publish
- methodology version and observation date;
- cohort definition before analysis;
- retailer/source list;
- raw row count and final deduplicated count;
- currency convention and any exchange-rate rule;
- median, 25th percentile and 75th percentile for sufficiently populated cohorts;
- downloadable or retained raw observation file;
- limitations, including inventory availability and any fields missing from retailer listings.