A cohort study examined the effect of anti-smoking advertisements on smoking cessation among a group of smokers. For the purposes of this exercise, we are focusing on two groups in the study: 1) an unexposed control group that consists of 18,842 individuals contributing 351,551 person-years to the study, and 2) an exposed group of 798 individuals contributing 14,245 person-years These exposed smokers saw anti-smoking advertisements 1 a month for several years. Nine cases of smoking cessation were identified in the unexposed group. One case was identified in the exposed group. Follow-up occurred for 21 years. For risk calculations assume all individuals were followed for 21 years.

Calculate the risk in the unexposed group