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 observed valid Near Mint offer. Thin markets with one or two active offers remain visible, but need at least three offers to enter signals and indices. 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

CardTrader

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

CardTrader catalogHourly 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. One or two observed offers are shown as a thin market; at least three are required for signals and indices. NO DATA means no valid active ask was observed.
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.
Game Market Index ENG / JAP: A permanent daily benchmark starting at 1,000. Each qualified CardTrader Near Mint card is weighted by the square root of price times visible offer depth, capped at 2% per card. Daily card returns are chain-linked; missing quotes carry forward and new cards enter without changing the previous level.
Index level: A unitless benchmark level, not a price. The 1,000 launch value is a readable starting convention; points and percentage change show whether the qualified market basket rose or fell.
One-copy basket: The current sum of one qualified copy of every index constituent. It is shown as a monetary reference but does not determine the benchmark level by itself.
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