Research methodology

One number cannot describe every card market.

TCGMarketWatch builds raw history from CardTrader active offers and keeps verified graded sales separate. Every comparison preserves source, timestamp, language, condition and currency.

Source roles

What each market observation means

Never blended silently

Raw reference

CardTrader

English/Japanese · EUR, ECB-normalized

The lowest valid Near Mint offer, published only when at least three active offers exist. Each language receives one daily observation.

An ask is supply evidence, not proof that a buyer completed a sale at that price.

Verified sold

eBay graded

Graded cards · USD

Ended graded comparables normalized by language, grading company, grade bucket and sale date.

Graded sold evidence is never blended into a raw-card reference.

Catalog identity

Bandai / OPTCG

Sets, cards and variants

Canonical codes, official expansion chronology, images, rarity and variant identity.

Catalog availability alone does not prove that current market prices exist.

Observed data lifecycle

From provider response to research metric

ArchiveRaw provider response is preserved for audit and replay.
NormalizeGame, set, card, variant, language, condition and currency are separated.
ValidateIdentity, freshness, outlier, listing and source-quality rules are applied.
DeriveReturns, volatility, index, relative strength and signals use only valid observations.

Refresh policy

OPTCG and Bandai catalogDaily discovery

CardTrader raw offersDaily snapshots

eBay graded cardsMonthly, selected cards only

Alerts and portfolioEvery six hours / daily

Exchange rateLatest ECB reference

Every valid daily card observation and every ENG/JAP Market Index snapshot is retained permanently. The interface exposes rolling windows without deleting the underlying history.

Currency comparison

USD and EUR values are stored in their original currencies. Display conversion uses the latest available ECB reference rate and never rewrites the source observation.

Offer-gap calculations convert all observations into the selected display currency before comparison and retain the original source currencies for audit.

Glossary

Read the terminal consistently

Raw price: Ungraded card reference for the specified printing, condition and language.
Floor: Lowest valid active CardTrader ask for the selected language and Near Mint condition. It is published only when the market contains at least three valid offers; otherwise the card displays NO DATA.
Sold comparable: Observed ended listing that passed card, language and grade matching.
Liquidity depth: Count of valid active asks; it measures available supply, not sales velocity.
One Piece Market Index ENG / JAP: Two permanent daily benchmarks built from English and Japanese CardTrader Near Mint floors backed by at least three valid offers. Missing quotes carry forward and new cards enter without changing the previous level.
Market regime: Observed classification combining Market Index direction, advancing breadth and median price variability; it is not a forecast.
Reference concentration: Share of the summed current raw references represented by the top-priced 1% of cards. It is not market capitalization.
Excess return: Card normalized return minus the One Piece Market Index ENG return on common observed dates.
Relative risk: A card profile based on observed volatility percentile, active-listing depth and maximum drawdown versus the tracked market.
Position scenario: A user-entered acquisition and exit model including quantity, shipping and fees. Break-even and maximum entry are arithmetic outputs, not forecasts or fair values.
Confidence: Coverage score based on CardTrader history depth, active offer depth, price-ladder consistency and freshness.
Snapshot: A provider observation stored with source time, capture time, currency and provenance.

Apply the methodology to live dataInspect source evidence, history and relative performance on every supported card.

Open One Piece market