The ‘Rotterdam-Antwerp effect’ is a term used to describe potential distortions in official trade statistics occurring as a result of misreporting of commodities passing through major world ports (such as Rotterdam in the Netherlands or Antwerp in Belgium) on their way to their final destination. This effect takes its name from the Dutch and Belgian ports because they are two of the largest ports in Europe, handling substantial volumes of trade in goods. However, it can occur at any transshipment port. In essence, the Rotterdam-Antwerp effect is an issue of trade data accuracy.
Within the context of UK trade with the Netherlands and Belgium, it has been argued that this effect overestimates the importance of these countries (and, by extension, the EU) as trading partners for the UK and therefore underestimates UK trade with the rest of the world. This project sought to obtain more precise estimates of the extent of transit flows via the Netherlands and Belgium in the UK data, and the characteristics of these flows. This is important as the UK seeks to establish an independent trade policy outside the EU.