Unknown Unknowns: We Need to Know How Many People Experience Imprisonment in Canada

Background: Understanding the size of a population is necessary to define the burden of disease, evaluate opportunities to improve health, inform service planning and assess demographic trends over time. Methods: In this article, we described available data on the number of admissions and number of people admitted to custody in Canada. We identified gaps in data, and described the potential value of these data for public health and health care purposes. Conclusion: We recommend the systematic collection and dissemination of relevant data on this population in Canada.