The next batch of data from the 2011 census was released yesterday—populations across the country broken down by age and sex.
I filtered the data for communities in Southwestern Ontario (population of 5,000 or more) to see which were the fastest growing and declining since the last census in 2006. I had to do this manually, so it's possible that someplace got overlooked, but here are some graphs taken from that data, with an emphasis on what Statistics Canada calls working age—the 15 to 64 group.
For these lists, I included communities in Windsor-Essex, Chatham-Kent, Lambton, London-Middlesex, St. Thomas-Elgin, Stratford-St. Marys-Perth, Huron, Grey, Bruce, Oxford, Norfolk, Haldimand, Brant-Brantford, Waterloo Region, and Guelph-Wellington.
At the top of the list, it's a sweep for Waterloo Region with all four top spots, and Cambridge also making the top 10. Guelph is in the top ten, as are communities in Bruce (Saugeen Shores), Oxford (Woodstock), Middlesex (Middlesex Centre) and Huron (Ashfield-Colborne-Wawanosh).
To round off the lists, here are the fastest growing communities for children and seniors. Woolwich, Wilmot and Wellesley score well across the board: