Saudi Arabia is leading by example within Opec when it comes to withholding crude oil from global markets in order to erode the stock overhang. The kingdom’s crude exports are set to fall to a seven-year low in 2017. And while this has been partially achieved by ramping up refining rates and thereby products exports, the total volume of liquids exported in 2017 is set to fall considerably.

The issue of how to monitor export volumes is likely to be a major topic of discussion at next...