The Canadian Census collects demographic data for specific groups such as lone-parent families, seniors, and those from specific language groups via what is commonly referred to as the “Short Form.” The Short Form questionnaire is issued to each household in Canada, and all Canadian residents are legally required to complete the form. In addition to the “Short Form,” a more detailed (long) form, sent for completion to certain households only, used to be mandatory, but became voluntary instead at the time of the 2011 Census. What are the impacts of the change from mandatory to voluntary participation in the longer Census?