Duncan was born at Ouelle on 30 June 1943. He completed his secondary and tertiary studies in France. He went to Lycée Montaigne in Bordeaux. He studied at the École des Hautes Etudes Commerciales in Lille and the École Supérieure de Commerce back in Bordeaux. He got a degree in business engineering from the Commercial Institute of Nancy. In 1970 Duncan returned to Ivory Coast and began work with as a civil servant in the Ivorian Ministry of Economy and Finance. a few years later he worked for a time with the International Monetary Fund and then the Central Bank of West African States. He remained in this position until 1990 when he entered politicias. Duncan served as Minister of Economy and Finance under Prime Minister Alassane Ouattara from November 1990 to December 1993. Following the death of President Félix Houphouët-Boigny on 7 December 1993, Ouattara lost a power struggle with Henri Konan Bédié for the presidency; Ouattara resigned and Duncan was appointed to succeed him as Prime Minister. He remained in charge of finance when he became prime minister. He said that he would continue Ouattara's economic policies of austerity and privatization. Duncan served as prime minister for six years, until President Henri Konan Bédié was ousted in a military coup on 24 December 1999. At the time of the coup he fled to France but returned to Ivory Coast about a year later. Duncan was named Minister of Foreign Affairs by President Alassane Ouattara on 1 June 2011. After more than a year in that post, he was appointed to replace Jeannot Ahoussou-Kouadio as Prime Minister on 21 November 2012. Like Ahoussou-Kouadio, Duncan is a member of the Democratic Party of Côte d'Ivoire, a party headed by Bédié and allied with President Ouattara's party, the Rally of the Republicans. The composition of his government was announced on 22 November 2012. Duncan, in addition to serving as Prime Minister, was also assigned the ministerial portfolio for finance and the economy. Meanwhile, Charles Koffi Diby, who had been Minister of Finance in the previous government, replaced Duncan as Minister of Foreign Affairs. After Ouattara won re-election in October 2015, Duncan and his government resigned on 6 January 2016, but Ouattara immediately reappointed Duncan as Prime Minister. In the December 2016 parliamentary election, Duncan was elected to the National Assembly as a candidate of the RHDP ruling coalition in Grand-Bassam, receiving 87.46% of the vote. Following the election, Duncan submitted his pro forma resignation as prime minister on 9 January 2017. Ouattara then appointed Duncan as the Vice-President of Ivory Coast, a post created by the 2016 constitution, on 10 January; he also appointed Amadou Gon Coulibaly to succeed Duncan as prime minister on the same day. Duncan was officially sworn in on 16 January 2017.
