Beyond military measures, the official Portuguese response to the "winds of change" in the African colonies was to integrate them administratively and economically more closely with the mainland. This was accomplished through population and capital transfers, trade liberalization, and the creation of a common currency, the so-called Escudo Area. The integration program established in 1961 provided for the removal of Portugal's duties on imports from its overseas territories by January 1964. The latter, on the other hand, were permitted to continue to levy duties on goods imported from Portugal but at a preferential rate, in most cases 50 percent of the normal duties levied by the territories on goods originating outside the Escudo Area. The effect of this two-tier tariff system was to give Portugal's exports preferential access to its colonial markets. The economies of the overseas provinces, especially those of both the Overseas Province of Angola and Mozambique, boomed.