It is worth discussing this result a bit. In absolute numbers (that is, simply counting up homicides), more children are killed by biological parents than by stepparents (341 versus 67 in Daly and Wilson’s study). But this is because only a small minority of children have stepparents. This pattern is especially true for young children, the most common victims of parental homicide. In 1984, only 0.4% of Canadian children one to four years old lived with a stepparent. To adjust for the fact that few young children live with stepparents, Daly and Wilson reported the data in Figure 14.35 as rates: the number of homicides per million child-years that parents or stepparents and children spend living together. Epidemiologists often summarize the results of such a study by reporting a relative risk. Here the relative risk of homicide in stepchildren versus biological children is the rate at which stepparents kill stepchildren divided by the rate at which biological parents kill biological children. For children zero to two years old, the relative risk of parental homicide for stepchildren versus biological children is about 70. This is an extraordinarily high relative risk. For comparison, the relative risk of lung cancer in smokers versus nonsmokers is about 11.