The $12.2 billion number comes from two reports that were issued by Justice Canada over the last couple of years. They look at the self-reported rates of intimate partner violence—and sexual assault in another study—and they calculate the number based largely on academic research, including the average number of women who end up in hospital and the average length of stay; the reports of lost work hours, the costs to the victim and to the employer; the cost of the use of victim services; the justice costs, the policing costs; and they calculate a cost for the suffering, which is a bit of a strange exercise but not atypical of economists. It is a way of assigning a value to the fact that these are victims who have suffered a violent crime.
On March 7th, 2017. See this statement in context.