IMO, if one is calculating yardages this tight you're just setting yourself up for a rant or something. I mean, 1/2 a yard??!! C'mon. With the deviations built into this game that's just crazy.
I guess those numbers were not all obtained from experiments on the course, otherwise you would not get such a perfect linear relation with a constant factor like 0.584.
One knows that wind affects distances, the simplest relation one can come with is a linear relation. You know that for 0mph wind, the distance is not affected. You try, from experiments on the course, to guess what happens for a perfect headwind of 20mph. Then you do the same for 10mph. From these 3 points, you can get the best linear relation and hope it works for other speed of the wind :) .
All these numbers above are summarized in the following formula: if D is the distance from the ball to the hole (I am talking about approach shots) and if D' is the distance corrected for the wind (I am talking about perfect headwind here), the formula which encode all those numbers above is
D' = D (1+V / 171)
where V is the speed of the wind in mph. 171 is the magic number found by the original poster. All linear relation between speed of wind and the additional distance you need to add can be written under this form (edit: only the magic number, 171 in this case, will be different).
Linear relation means that if you double the speed of the wind, you double the distance to add (it's not obvious that this relation is linear!). Indeed, the relation I wrote above can be written as
deltaD = D' - D = D V / 171
deltaD being just the additional distance. Written like that, if you double V, you double deltaD.