Method & sources

How the numbers on this site are collected, checked and shown.

Sources

• World Bank Remittance Prices Worldwide. Every quarter the World Bank surveys what providers charge to send the equivalent of USD 200 and USD 500 across several hundred corridors: the fee, the exchange rate applied, and how far that rate sits from the interbank rate. Used under CC BY 4.0. The World Bank does not endorse this site.
• European Central Bank euro reference rates, collected three ways: the SDMX data API, the daily XML file and the public web page. The web page is read with CSS selectors, the way a scraper reads any page, and checked to the last digit against the other two.

How a number gets here

1. A collector fetches each source on its own schedule. It identifies itself, reads robots.txt first, waits between requests, and asks conditionally so an unchanged file is not downloaded again. If a site refuses, the run is recorded as blocked and left alone.
2. The response is kept exactly as received, named by its SHA-256 hash: the evidence.
3. An extractor reads the observations out of it and publishes them as events on Kafka. Every observation carries the run that produced it and the hash of its evidence.
4. The catalog checks every price before storing it. The strongest checks are identities the numbers must satisfy: total cost equals fee plus exchange-rate margin; the margin equals the gap between the provider's rate and the interbank rate. A small breach is flagged; a large one holds the price back.
5. Channels that publish the same rate are reconciled daily, and every value a source later changes is kept as a revision.

Reading the checks

• better-than-interbank the provider applied a rate better than interbank: usually a first-transfer promotion or a parallel-market rate. Real, but not an everyday price.
• rate-not-disclosed the provider did not say what rate it applies, so the true cost may be higher than shown.
• margin-unverifiable the source published the rates with too few digits for the margin to be checked.
• margin-identity / cost-identity the source's own numbers disagree with each other by more than rounding.