How rankings work
Best-Sellers.org does not estimate sales counts when sales counts are unavailable.
Four different signals
We keep these labels honest. They are not interchangeable.
- Retailer bestseller rank — a source's own ranked list, attributed to that source, with observation time, browse-node/category context, and provenance. Amazon sales ranks imported from the official Creators API are
RETAILER_SALES_RANK. - Best-Sellers.org Score — an independent 0–100 metric (BSS-V1) built only from documented retailer-rank inputs. It is our score, not an Amazon score and not a sales-count estimate.
- Search trend — relative Google search interest from the official Google Trends API when access exists. It is not a sales count, not a retailer rank, and not an absolute “12,458 searches” figure unless the API returns a true count (it does not).
- Rank movement — change in observed rank between comparable snapshots. Lower numeric rank is better. Movement is not volume.
- Price information — observed offer prices and currency, never invented, and not treated as proof of popularity in BSS-V1.
Amazon category context
#2 in Electronics > Headphones is not #2 on Amazon overall. Every observation keeps its browse-node list. WebsiteSalesRank, when present, is stored as its own root-node context and is never flattened into a fake global list. Search result order from the Creators API is discovery only and is never stored as a sales rank.
Sales rank is not unit sales quantity. eBay Browse remains catalog/offer/price only — eBay search position is never a ranking input.
History begins when we observe it
Daily snapshots are built from our own observations. We do not backfill fake Amazon history. The first date in the archive is the first date we have a legitimate snapshot. Average rank is not “average sales.”
Movement rules
- 27 → 9 is up 18 positions.
- 4 → 11 is down 7 positions.
- A first appearance is a new entry only when the prior comparable snapshot is complete.
- A missing product is not observed unless list coverage is complete enough to prove an exit. We do not say “fell out of chart” from an incomplete refresh.
Trend Momentum Score (TMS-V1)
TMS is independent of Best-Sellers.org Score. Weights: 7-day growth 0.26, 30-day growth 0.20, acceleration 0.22, baseline breakout 0.15, persistence 0.08, freshness 0.05, confidence 0.04. Growth uses a median baseline and a floor so 1→3 cannot become an “explosion.” Official API series use consistent scaling and may be compared with each other; independently scaled 0–100 website series cannot. US geography is labeled as United States, never worldwide. A stale series cannot remain Exploding. Seasonal rises that match a prior-year window are labeled Seasonal surge, not a brand-new explosion.
Price Intelligence
A price is stored only from a legitimate provider response. We never invent MSRP, sale price, shipping, coupons, or “lowest ever.”
- Current observed price — the latest eligible offer amount we recorded, with currency, retailer, source, and time.
- Total delivered price — item plus shipping when shipping is known. Unknown shipping is shown as “+ shipping” and is not silently compared to delivered totals.
- Lowest observed by Best-Sellers.org — the lowest amount in our history. That is not a retailer all-time low unless we have full historical coverage (we do not claim that).
- Stale offers — remain in history. They are not current buy recommendations after the freshness threshold.
- Condition — New and used are never merged. Budget boards default to New so a cheap used listing cannot qualify as an under-$25 new product.
- Budget inclusion — Under $25 means current eligible USD price ≤ 25.00. Delivered price is preferred when known.
Price Opportunity Signal, when present, compares a fresh price to recent medians. It is not a Best Sellers Score input and is not treated as popularity.
No data means no score
Best-Sellers.org Score is calculated only when real retailer-rank observations exist. Every calculated score keeps its version, calculation time, component values, source inputs, confidence, and explanation. BSS-V1 excludes search trends and price-as-popularity. BSS-V2 is stored but dormant until enough high-confidence product-linked TMS rows exist.
What we will not do
- Convert “popular,” “trending,” “highly reviewed,” or “search result” into “best selling.”
- Invent units sold, review counts, or “X people bought this.”
- Scrape Amazon or any other retailer, or bypass access controls.
- Generate thin SEO pages just because a category and budget can be combined.