Europe’s main regulators are collating data from the region’s exchanges, trading platforms and banks on the size of their dark pools to understand how much trading goes on away from transparent exchange order books.

The Committee of European Securities Regulators is set next month to report its findings to the European Commission which will then use this data in its review of Mifid, the 2007 trading directive. This could lead to new rules being drafted in Mifid II, perhaps as early as next year.