The Crypto Times Korea USDT Premium Index · the Kimchi Premium · daily fix 11:30–12:30 KST · CTPI-USDT-SPOT-KRW

Methodology v0.1.0 · DRAFT pending calibration and Owner sign-off. Values marked TO BE SET are filled from calibrate.py after roughly 44 hours of live capture; the version number does not change when they are filled, because filling them does not change how a fix is computed.

What is measured

The Crypto Times Korea USDT Premium Index (CTPI-USDT-SPOT-KRW) measures the “kimchi premium” on the dollar stablecoin USDT: how much more (or less) a USDT costs in Korean won on Korean exchange order books than the global dollar price converted at the reference exchange rate, every trading day. Two numbers are published: the raw premium (won price of USDT versus USD/KRW — the figure most trackers quote) and the peg-adjusted premium (the headline), which also divides out USDT’s own small deviation from $1 so that only the Korea-versus-world gap remains.

The daily fix

Fix window 11:30–12:30 KST (12:00 ± 30 minutes), published at 12:31 KST (03:31 UTC) by a systemd timer with Persistent=true; if the host is off through the window, the timer runs on boot, finds no samples and refuses to publish. No estimate is ever published in place of a missed fix; a missed or late fix is recorded in the corrections log as a publication-timing entry.

Official fixes are computed every Monday to Friday (KST). Local public holidays do not pause the index: crypto trades every day, so a Korean public holiday is an ordinary fix day, priced against the ECB reference rate by the usual rule below. Weekend runs store an indicative point at the same fix time, measured against the last business day’s USD/KRW and marked distinctly on the chart.

Inputs

• Venue quotes: the USDT/KRW order book of each constituent exchange, sampled every 60 seconds during Korean market hours (08:00–23:59 KST) and every 300 seconds overnight. Each sample’s raw payload is stored verbatim and never modified.
• USDT/USD reference: Kraken spot USDT/USD best-bid/best-ask mid, sampled on every collector pass, seconds before the venue books.
• USD/KRW reference: the ECB euro foreign exchange reference rate cross (EUR/KRW ÷ EUR/USD), published by the ECB around 16:00 CET on TARGET business days under a permissive licence — about 00:00 KST the next day, so a noon-KST fix uses a rate roughly twelve hours old. Its date is cited with every fix. The rate may be carried across weekends and holidays for at most 5 calendar days; beyond that an official fix refuses.

Why the family pairs every sample with its own reference

The engine that computes this index also computes The Crypto Times India Bitcoin Premium Index, where the global leg moves inside the window; the family rule pairs each venue sample with the reference captured nearest to it in time (within 120 seconds; unpaired samples are counted and dropped, never estimated). For a stablecoin leg the pairing changes nothing materially — USDT/USD moves by basis points — but one rule for the whole family is worth more than two.

Computation

1. For each paired sample: r = venue_mid_krw ÷ usdtusd_ref — the USD/KRW rate implied by that venue’s USDT quote.
2. Per venue: the median of r across its paired samples is the venue observation; the median two-sided won depth resting within ±TO BE SET bps of mid (stored bands: 50, 100) is the venue weight.
3. Eligibility: a venue is excluded if it is shadow-listed, has fewer than 2 paired samples in the window, has zero in-band depth, or its depth is below the floor of ₩TO BE SET two-sided. Exclusions are recorded in the fix’s provenance with the venue’s would-be value.
4. Aggregate: the depth-weighted median of the venue observations, R. A venue must supply real resting depth, not just a printed price, to move the fix.
5. Peg-adjusted premium (headline): premium_pct = (R ÷ USDKRW − 1) × 100.
6. Raw premium: raw_premium_pct = (observed_mid_median ÷ USDKRW − 1) × 100, where the observed mid median is the depth-weighted median of venue median won mids.
7. Published price level: value = R × usdtusd_ref (won per USDT), where usdtusd_ref is the median of the references actually paired, so that value ÷ (usdtusd_ref × USDKRW) − 1 reproduces the headline premium exactly from the figures on the page.

Publication gates

An official fix requires at least TO BE SET eligible venues, a publishable USD/KRW reference within the carry ceiling, at least one paired USDT/USD reference, and no existing official fix for that time. Officials are immutable once written; restatements go only through governance tooling and appear in the corrections log.

Quality flags (published with the fix, never hidden)

two_venue_aggregate; high_venue_dispersion when venue observations differ by more than TO BE SET bps; unpaired_samples(n); insufficient_venues on indicative fixes only.

Constituents and venue disclosure

Candidate venues at launch: Upbit, Bithumb, Coinone, Korbit. Constituent status is set from measured order-book data during calibration and reviewed against the family venue policy; regulatory action against a venue (suspension, enforcement) is disclosed on the page beside the fix — the per-exchange table states which venues the number includes and why any is excluded, every day. Changes appear in the changelog.

Live indicative readings

Between fixes the page shows a 5-minute indicative reading computed with the same pairing and aggregation, against the USD/KRW rate in force at the sample. Past 15 minutes without a usable sample the live block shows STALE rather than a stale number. Indicative readings are never part of the daily fix series.

The family’s synchronized reading

Besides the daily fix, the engine records one reading a day at 12:00 UTC — the same moment for every index in the family (21:00 KST here) — computed exactly as above over 11:55–12:05 UTC (20:55–21:05 KST), against the latest ECB reference captured before the window closes, which is always the prior business day’s rate. It exists so that a future multi-country composite can combine markets observed at the same instant rather than hours apart. It is not this index’s official value and is never part of its fix series; a day on which it cannot be computed is recorded as INVALID with its reason. Around that window the collector samples every 60 seconds whatever the local hour. The series is published at /v1/sync on the engine host.

Versioning

The methodology version changes only when the way a fix is computed changes — never for display, documentation or the filling of calibration values above. Package versions are separate.

2026-09-24 · engine v1.12.3 · methodology v0.1.0 (draft)

Methodology text: Local public holidays do not pause the index: a holiday is an ordinary fix day, priced against the ECB reference rate by the usual rule; weekends stay indicative. No change to how the fix is computed. Official fixes remain switched off.

2026-09-23 · engine v1.0.0 · methodology v0.1.0 (draft)

Index created on the CTPI family engine (the same code that runs the India Bitcoin index), configured for USDT/KRW: Korean venues Upbit, Bithumb, Coinone and Korbit; USDT/USD reference from Kraken paired per sample; ECB USD/KRW denominator; noon-KST fix published 12:31 KST; raw and peg-adjusted premiums. Official fixes remain switched off ([fix].official_enabled = false) until calibration values are set from live data and the methodology is signed; the daily timer stores indicative (shadow) fixes meanwhile.

No corrections, restatements or publication-timing entries yet. Entries are added here, inside this document, never on a separate page: a missed or late fix is recorded as a publication-timing entry; a change to a published value is a restatement, with the old value, the new value, the reason and the date.

Date	Type	Fix date	Detail
none recorded

The daily fix series to date. Full series JSON with a stable schema: /v1/fixes.json.
CSV JSON

The difference between the price of a crypto asset on Korean exchanges, in won, and its global dollar price converted at the exchange rate. It has been a feature of Korean markets since 2017 and is the most-quoted regional price signal in crypto. This index measures it on USDT — the stablecoin that dominates Korean won trading — so that the number isolates dollar demand rather than Bitcoin’s own moves.

Korean capital-control and real-name banking rules structurally constrain arbitrage: foreigners are effectively locked out of won exchanges and outbound capital faces reporting frictions, so a premium cannot be arbitraged away instantly. It has ranged from double digits in 2024 to under 1% in 2026, and has gone negative.

Peg-adjusted. The raw premium compares the won price of USDT with USD/KRW; the peg-adjusted premium also divides out USDT’s own small deviation from $1, so only the Korea-versus-world gap remains. Both are published every day; the raw number is the one most trackers quote.

Candidate constituents are Upbit, Bithumb, Coinone and Korbit. Constituent status is set from measured order-book depth during calibration and reviewed against the published venue policy. Regulatory action against a venue is disclosed beside the fix: the venue-status line and the per-exchange table state, every day, which venues the number includes and why any is excluded.

No. These are public, on-exchange order-book prices on licensed Korean venues. The premium is a market phenomenon, not an unofficial exchange rate.

Crypto trades every day. Official fixes run Monday to Friday, and local public holidays do not pause the index: a holiday is an ordinary fix day, priced against the ECB reference rate by the usual rule. The ECB reference does not update at weekends, so weekend readings are published as indicative, measured against the last business day’s USD/KRW, and marked distinctly on the chart.

The per-exchange table shows sampled order-book best bid and ask — tradeable quotes at sample time, subject to depth and fees. The index value itself is a computed benchmark, not a quote.

Same engine, same methodology family, same ECB denominator, own venues and own timezone. The indices are published separately and this page makes no cross-index comparison.

The citable number is the once-daily fix. A live indicative reading updates continuously above it and is never part of the daily fix series.