# What is a trade anomaly?

An anomaly is an unusual movement in a reported exporter-to-importer-product trade series. It is a research prompt, not a cause, forecast, buyer signal, or guarantee.

## The identifiers

- **Exporter:** the country from which the goods were shipped.
- **Importer:** the receiving country or market.
- **HS6:** the six-digit product classification.
- **Route:** exporter + importer + HS6 product.
- **Year:** the reporting year.

## How the values are calculated

- **Market imports:** Reported imports into the buyer market for the HS6 product and year.
- **Exporter market share:** exporter trade value / buyer-market imports x 100.
- **Year-on-year momentum:** (current value - previous value) / previous value x 100.
- **Momentum acceleration:** current momentum minus previous momentum.
- **Three-year CAGR:** (ending value / starting value)^(1 / years) - 1.
- **Anomaly z-score:** a standardized distance from the comparison baseline. It is not a probability.
- **Anomaly type:** source-provided direction such as spike or drop.
- **Anomaly severity:** source-provided signal strength, not a probability.
- **Market HHI:** sum of squared supplier market shares.
- **Volatility CV:** standard deviation / average of the observed route series.
- **Maximum drawdown:** largest percentage fall from an earlier peak.

The upstream threshold and comparison window used to assign anomaly type, severity, and z-score are supplied by the published data source. This guide does not invent a threshold or present the signal as causal proof.

[Open the live route example](https://www.yugalinks.com/trade/signal/anomaly/gbr-bra-853110)


## Data sources

- Primary trade series: OECD (2025), Balanced international merchandise trade statistics (BIMTS) - HS2017-6D, OECD Data Explorer (accessed on 2026-09-03). [OECD Data Explorer](https://data-explorer.oecd.org/) - [OECD Terms & Conditions](https://www.oecd.org/termsandconditions/)
- CEPII BACI bilateral trade flows (202601): [dataset page](https://www.cepii.fr/CEPII/en/bdd_modele/bdd_modele_item.asp?id=37) - [BACI documentation](https://www.cepii.fr/DATA_DOWNLOAD/baci/doc/baci_webpage.html) - [Etalab 2.0 Open Licence](https://www.etalab.gouv.fr/wp-content/uploads/2018/11/open-licence.pdf)

This page presents derived Yugalinks views of reported observations and calculated indicators.