The Rotterdam-Antwerp effect.
For clarification, again:
From the ONS..
“Summary
Annually, the Netherlands is the UK’s third largest trading partner in the EU. There are legitimate, proven reasons as to why trade with the Netherlands is high, even relative to its population. It is also reasonable to assume that trade with the Netherlands suffers from an element of distortion. However, it is not possible to estimate, with any certainty, the impact that the Rotterdam effect has on UK Trade with the Netherlands and its subsequent impact on UK Trade with EU and non-EU countries.
Estimates can, however, be based on certain assumptions. The most likely assumption indicates that UK exports to EU countries account for somewhere between 46.1% and the currently published (for 2013) 50.4% of total UK exports, if the Rotterdam effect was considered. Similarly, UK imports from EU countries account for somewhere between 49.1% and the currently published 53.3% of total UK imports.
We also remind users that UK trade estimates are produced in line with international standards and that, ultimately, the port of Rotterdam is not unique and that other ‘gateways’ could counter the impact of the Rotterdam effect.”
ONS REPORT ON THE ROTTERDAM EFFECT 2016
The Rotterdam Effect is essentially unquantifiable. Do not be fooled into thinking it can – by either side!