The iGuide Supply Grade — Our system for rating scarcity

The iGuide Supply Grade is a ranking system for rating the scarcity of personal property including art, antiques, collectibles, and other real assets. First developed in October 1998 for Warren's Movie Poster Price Guide, it's a letter grade from A+ to F. The grade represents our opinion of the rarity or relative availability in the marketplace after applying criteria in our supply ranking analysis. The methodology involves evaluating and ranking supply levels without considering market demand. It focuses solely on the availability of an item relative to other items in the target market. We consider factors like sales velocity, customer interest, market trends, and price fluctuations. We utilize real sales data, tracking price changes and sales volume to assess whether an item is in high, moderate, or low supply based on actual market behavior. Our goal is to help market participants gauge rarity in order to make better buying, pricing, and marketing decisions.

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A+

10 on a scale of 1 to 10.
(extremely rare) Unique or less than 5 known to exist.

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A

9 on a scale of 1 to 10.
(very rare) Rarely available for purchase, once a decade.

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A-

8 on a scale of 1 to 10.
(rare)

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B+

7 on a scale of 1 to 10.
(very scarce) Hard to find. Not readily available, requires effort to obtain.

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B

6 on a scale of 1 to 10.
(scarce) Relatively uncommon, but can be found with some searching.

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B-

5 on a scale of 1 to 10.
(somewhat scarce)

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C

4 on a scale of 1 to 10.
(common) Numerous examples available for purchase every day.

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C-

3 on a scale of 1 to 10.
(very common) Common and with little if any demand

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D

2 on a scale of 1 to 10.
(extremely common)

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F

1 on a scale of 1 to 10.
(utterly common) Endless supply, 0 demand. Trash, junk, swill, give to Goodwill

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There are many different systems in economics for rating the supply. Here are a few of them:
Diffusion of Innovation (DOI) Curve: This model ranks demand by adoption stages: Innovators, Early Adopters, Early Majority, Late Majority, and Laggards.

S-curve Model: Describes product adoption in terms of low initial growth, followed by rapid growth, and then a plateau. This helps track demand over time.

Sales Data-Based Rating Systems

Sell-through Rate (STR): Measures the proportion of inventory sold within a specific period. Higher STR means stronger demand.

Weeks of Supply (WOS): Measures how long current stock will last based on current sales rates.

Stock Turnover Rate: How quickly stock is replenished and sold, indicating high or low demand.

Consumer Sentiment Indicators

Net Promoter Score (NPS): While originally used for customer satisfaction, a high NPS can also signal strong demand for products that people are likely to recommend.

Search Engine Data & Social Media Trends: The number of searches or mentions on platforms like Google, Twitter, or Instagram is often used to predict demand surges.

Demand Forecasting Models

Quantitative Forecasting: Uses historical data to predict future demand, such as time series analysis or regression models.

Qualitative Forecasting: Relies on expert opinion, market research, and surveys to gauge demand.

Retail-Specific Ratings

ABC Analysis: Ranks products based on sales volume. Category A items have the highest demand, B moderate demand, and C the lowest.

Pareto Analysis (80/20 Rule): Identifies that 20% of products often generate 80% of demand and revenue.

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