durham population
â¢ The Durham Region population in 2015 was estimated to be 661,190 . â¢ The largest municipality in Durham Region is Oshawa with an estimated population of 164,260 in 2015. â¢ The Durham Region population increased by 15% between 2005 and 2015, higher than the increase in Ontario of 10%. â¢ The largest population growth in Durham Region between 2005 and 2015 was seen in Ajax, with an increase of 30%, followed by. Whitby with an increase of 19%.