we might report either a 2% increase in absolute risk, or a relative risk of 0.87/0.85 = 1.02, that is a 2% relative increase in risk. The odds in the two groups are given by 0.87/0.13 = 6.7 and 0.85/0.15 = 5.7, and so the odds ratio is therefore 6.7/5.7 = 1.18: exactly the same as for bacon sandwiches, but based on very different absolute risks.
