Methodology and Calculation
Sources, calculation basis, and update policy for the rates yensend.jp displays
1. Data Source
Provider remittance quotes shown on this site are retrieved from the Wise public comparison API (/v4/comparisons/). This API is publicly accessible without authentication (source: docs.wise.com). It returns rates, fees, receive amounts, and delivery times for providers aggregated by Wise. For Taiwan TWD, yensend additionally uses the Bank of Taiwan official JPY/TWD spot buy/sell midpoint as the mid-market reference baseline.
2. Total Cost Formula
Total cost = send amount − (receive amount ÷ mid-market reference rate). This single number expresses the actual yen lost to fees and FX margin combined. Most corridors use the explicit mid-market row returned by Wise where `isConsideredMidMarketRate: true`. Taiwan TWD uses the Bank of Taiwan official JPY/TWD spot buy/sell midpoint because Wise may omit its own mid-market row on that lane.
3. Freshness Gate (45-Minute Rule)
Each provider row shows Wise's collection timestamp (dateCollected). Because pages can be served from the CDN cache for up to about 35 minutes, any row whose data may be more than 45 minutes old by the time you view it is labeled "Data delayed" and is not treated as current (Japan Act against Unjustifiable Premiums and Misleading Representations Article 5(1), preventing misleading-superiority claims / internal policy F-039). Rows more than 6 hours old when the page is generated, and rows with missing or NaN timestamps, are not shown.
4. Cache Policy
To avoid overloading the Wise API, caching runs in two layers. (1) Wise responses are stored in Upstash Redis using a Stale-While-Revalidate (SWR) pattern: a response is fresh for 60 seconds and stale until 180 seconds, and a stale response is served immediately while a background refresh runs. Only when the Wise API is failing do we fall back to a stored value up to 30 minutes old. Single-flight locking via Redis SETNX prevents stampedes. (2) The comparison pages (the home page and each destination page) are cached at the CDN for about 30 minutes (up to about 35 minutes while the cache is being refreshed), so the board updates about every 30 minutes. Each row shows when its rate was fetched, and the top of the page shows how long ago the data was retrieved.
5. Ranking Criteria
Providers are sorted by total cost (fee + FX margin combined) ascending. Ties are broken by provider name ascending (partner-neutral D-026). Partner versus non-partner status does not affect ranking. The first-place provider receives a "Rank 1" badge, but this reflects only the result at the current display moment and does not guarantee rankings at future times, other amounts, or other corridors.
6. Advertising and Affiliate Fees
This site is a comparison information service. We may receive referral fees from some providers, but they do not influence display order or content (D-026 partner-neutral ranking). Providers with active partnership are marked with a "Partner" label inline for transparency. This site is not a fund-transfer operator and does not handle remittance services (Payment Services Act Article 2(2) and 2(3)).
7. Limitations
(a) Only the JPY → PHP corridor has Lane A measured verification data (2026-04-17, fact-registry F-001), which displays as a "Verified" label on the Wise row. VND / KRW / NPR / CNY / Taiwan TWD provider quotes rely on timestamped data via the Wise public API or Wise official pages without provider-native independent verification; the CNY route gate is recorded as fact-registry F-070. For Taiwan, provider quote availability is recorded as F-072 and the independent Bank of Taiwan reference midpoint as F-073. (b) Displayed provider rates are Wise-aggregated values and may differ slightly from each provider's official site. Always confirm at the provider's site before sending. (c) Delivery times are Wise-recorded estimates and vary based on FX, receiving bank hours, and remittance channel.
8. Sources and Reference Documents
Wise API documentation: docs.wise.com / Wise public comparison API: api.wise.com/v4/comparisons/ / Internal fact-registry: scripts/fact_registry.json (F-001 onward cumulative entries; see scripts/fact_registry.json for the current count) / Lane A measurement log: domain_knowledge/24_wise_api_lane_a_results.md. GitHub: github.com/dongmin7208/remittance-compare (private).