Auction Comp Average
We track every sold listing on Bring a Trailer and Cars & Bids — hundreds of real Porsche 911, Boxster, and Cayman auction results. The p90-filtered average of these sales is the comp baseline.
Current Asking Prices
Every 2 hours we scrape live asking prices from BaT, C&B, Carvana, Cars.com, and PCarMarket. The average of all active listings (filtered to $10k–$500k) is the market price.
The Formula
FSMI = comp average ÷ asking average × 100. When asking prices fall below historical comps, the index rises above 100. When asking prices exceed comps, it drops below.
FSMI = (comp_avg / avg_asking) × 100
What it Means
FSMI
Market
> 105
Strong Buyer's Market
100–105
Buyer-Favorable
95–100
Balanced
90–95
Seller-Favorable
< 90
Seller's Market
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