Carstens leaves Mexico’s central bank after 'challenging' period The outgoing head of Mexico’s central bank, Agustin Carstens, says there would be trade with the United States even without the NAFTA treaty, but that there could be "some kind of complication" in the short term. Carstens, 59, will leave the central bank at the end of November to run the Bank for International Settlements. IMAGES AND SOUNDBITES