On another thread we were discussing (veering from topic actually) higher proof off the still. Perhaps a discussion on how that works.
Column stills used by the majors are run continuously, which is to say alcohol laden mash is constantly fed into the top and as is falls down rising steam strips out the alcohol which rises as vapor to the top to be drawn off while water and mash solids run out a drain in the bottom. A full description is more complicated but that's basically the idea.
A column still can be set to bring off the alcohol vapor with an alcohol by volume (ABV) as high as 195 proof which is almost pure alcohol. Vodka is 190 proof which is almost odorless, colorless and tasteless at that point which is why the regulations limit Bourbon to 160 proof to make sure the vapor contains enough flavoring elements to age into the characteristic flavor of Bourbon. Of course lower still proof has more flavor, that's the reason Stitzel -Weller brought the new whisky off the stills and into the barrel at 105 proof. Wild Turkey was 103 at one time for the same reason.
The reason a distiller sets the still at 140-160 proof is because over the course of a working day that will produce 40-60% more beverage alcohol than would be had at 100 proof. Profit, pure and simple.