Duncan is located close to the center of Oklahoma. Duncan is between the Stephens, Comanche, Cotton county. Duncan has 43.11 square miles of land area and 4.87 square miles of water area. As of 2010-2014, the total Duncan population is 23,364, which has grown 3.82% since 2000. The population growth rate is much lower than the state average rate of 10.67% and is much lower than the national average rate of 11.61%. Duncan median household income is $40,171 in 2010-2014 and has grown by 32.26% since 2000. The income growth rate is lower than the state average rate of 38.43% and is higher than the national average rate of 27.36%. Duncan median house value is $95,800 in 2010-2014 and has grown by 62.37% since 2000. The house value growth rate is about the same as the state average rate of 62.66% and is higher than the national average rate of 46.91%. As a reference, the national Consumer Price Index (CPI) inflation rate for the same period is 26.63%. On average, the public school district that covers Duncan is better than the state average in quality. The Duncan area code is 580.