The difference in incidence rate between exposed and unexposed populations, expressed in absolute terms. It is calculated by subtracting the incidence rate in the unexposed group (10) from the incidence rate in the exposed group (II). 10 can be interpreted as the baseline incidence rate, and only the incidence rate exceeding this figure is due to exposure. Therefore, the rate difference is also known as attributable rate. A difference in incidence rate of 0 means that the disease is not related to exposure (II = 10).