BC.. Interesting calculations. I am not sure if .16% or .07% would be the 'reduced' risk, however. Subtracting 75% away from .28% is .25*.28 = 0.07%. But increasing a .16% risk by 75% would bring it to 1.75*.16=.28%. So it depends on how you look at it. It depends on what it means to 'reduce a risk by 75%'. The first interpretation (.25*x) makes the most sense to me, since we are subtracting 75% of the original risk from the original risk. As a check, reducing by 100% would give us 0. On the other hand, the method that gives .16% has the risk become 57% of what it was. If we were to use this method to find a 100% reduction, we would do 2*x=.28... x = .14%. I can't see reducing a risk by '100%' meaning something other than being risk free! But maybe I am unaware of a convention?