Methodology
How OP Box Index reads One Piece market signals
Research and data: OP Box Index · Published · Updated · Data sources & methodology
OP Box Index is built to make sealed One Piece booster box research easier to read. The site does not issue buy or sell calls. It organizes public marketplace signals so collectors can compare sets without jumping between many tabs.
No single market number
This site used to publish a composite index that rolled every Japanese box into one figure. We removed it in July 2026. The problem was not the arithmetic — it was that a single number papered over sets moving in opposite directions, and it drifted away from what the underlying per-set data actually said. We would rather show nothing than show a number we cannot stand behind, so the site now reports each set on its own and lets you read the spread yourself.
The same rule governs everything below: a blank is better than a wrong number. Where a value is not yet verified we mark it “collecting” rather than estimating it.
Grading population, by grader and by printing
Grading population shows how much submission activity has reached each grader's report. Every graded card originated in an opened product, but a weekly addition may be a recent pull or a card held raw before submission. We therefore treat population growth as an indirect collector-activity signal, not a count of boxes opened. We read PSA population through GemRate's set-level aggregation and CGC and TAG from each grader's own report, and keep their scales separate: PSA tops out at 10; CGC splits its top grade into Pristine 10 and Gem Mint 10 (plus the retired Perfect 10); TAG splits its top grade into 10 and 10P.
We also never sum across printings. The Japanese and English releases of a set are different print runs with different pull rates, and merging them makes the gem rate meaningless. Every figure on the grading page is labelled by edition. As of the latest collection, PSA has graded 583,430 cards from Japanese sets and 594,907 from English sets across the sets we track — two separate figures, deliberately not added together.
Counts are collected weekly and appended to a ledger that is never rewritten, so week-over-week change is measured against what we actually recorded at the time rather than back-filled after the fact. Weekly history is published from 2025-12-03 onward; we do not reconstruct earlier weeks we did not observe.
Box price bands
For each sealed box, the site separates low, middle and high price bands when enough market references exist. The middle value is useful as a quick reference, but the spread matters too. A tight spread is usually more reliable than a wide spread with one unusually cheap or expensive listing.
Where we have enough completed sales, the sold median takes priority over any listing band. A concrete example of why: on the day we wrote this, Japanese OP-05's cheapest verified listing ($151.89) sat 28% below its sold median ($211), while Japanese OP-06's cheapest listing ($192.38) sat 67% above its sold median ($115). Listings alone would have ranked the two boxes in the wrong order.
Verified lowest listings
Lowest-price buttons are filtered so loose packs, unrelated products, wrong languages and suspiciously low listings are less likely to appear. When a listing cannot be matched confidently, OP Box Index hides the direct button or falls back to a broader search.
Chase-card concentration
Some sets are carried by one major card. Others have several cards with strong demand. A box can be more resilient when value is spread across multiple chase cards, because demand does not depend on a single pull.
PSA 10 and population context
PSA 10 prices are treated as a separate graded-card market. A high PSA 10 price can signal premium collector demand, but thin sales samples are handled carefully. If the match is uncertain, the price is not shown as a confirmed market value.
Why some prices are hidden
Missing data is intentional when the match quality is weak. Showing no price is better than showing the wrong card, wrong language or wrong product. This is especially important for manga rares, alternate arts and special cards where small title differences can mean a large price difference.
How to use the signals
- Use sold prices to judge real demand.
- Use active listings to understand current purchase options.
- Use chase-card data to understand what supports sealed demand.
- Use PSA data to judge premium-card strength.
- Use seller and condition checks before buying anything.
Start with the live market dashboard, then open a set guide for stable background context, or see grading population by set and edition.