clemlais

You will need to monitor your positions (both long and short) and transfer the margin accordingly between each account.

From wikipedia:

The English dramatist Philip Massinger used the phrase "black list" in his 1639 tragedy The Unnatural Combat.[3]

After the Restoration of the English monarchy brought Charles II of England to the throne in 1660, a list of regicides named those to be punished for the execution of his father.[4] The state papers of Charles II say "If any innocent soul be found in this black list, let him not be offended at me, but consider whether some mistaken principle or interest may not have misled him to vote".[5] In a 1676 history of the events leading up to the Restoration, James Heath (a supporter of Charles II) alleged that Parliament had passed an Act requiring the sale of estates, "And into this black list the Earl of Derby was now put, and other unfortunate Royalists".[6]

Edward Gibbon wrote in The History of the Decline and Fall of the Roman Empire (1776) of Andronicus that "His memory was stored with a black list of the enemies and rivals, who had traduced his merit, opposed his greatness, or insulted his misfortunes".[7]

For the same reason the Flynn effect exists I guess. Most immigrants come from less developed countries so should have a lower IQ on average.