In 1970 Duncan returned to Ivory Coast and began work 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.

[4] Duncan served as prime minister for six years, until President Henri Konan Bédié was ousted in a military coup on 24 December 1999.

Duncan was named Minister of Foreign Affairs by President Alassane Ouattara on 1 June 2011.

Duncan, in addition to serving as prime minister, was also assigned the ministerial portfolio for finance and the economy.

[8] Following the election, Duncan submitted his pro forma resignation as prime minister on 9 January 2017.